One-side-protected polarizing film, pressure-sensitive-adhesive-layer-attached polarizing film, image display device, and method for continuously producing same

ABSTRACT

The present invention pertains to a one-side-protected polarizing film having a transparent protective film on only one surface of a polarizer, wherein: the polarizer contains a polyvinyl alcohol-based resin, has a thickness of 10 μm or less, and is designed to have a single-body transmittance T and a polarization degree P representing optical properties satisfying the condition of the following formula: P&gt;−(100.929T−42.4−1)×100 (provided that T&lt;42.3) or P≥99.9 (provided that T≥42.3); and the other surface of the polarizer has a transparent layer having a compressive elastic modulus at 80° C. of 0.1 GPa or more. Even when the polarizer has prescribed optical properties and the thickness is 10 μm or less, this one-side-protected polarizing film is capable of suppressing the occurrence of through cracks and nano-slits.

TECHNICAL FIELD

The invention relates to a one-side-protected polarizing film includinga polarizer and a transparent protective film provided on only onesurface of the polarizer and to apressure-sensitive-adhesive-layer-attached polarizing film including theone-side-protected polarizing film and a pressure-sensitive adhesivelayer. The one-side-protected polarizing film and thepressure-sensitive-adhesive-layer-attached polarizing film may be usedalone or as a component of a multilayer optical film to form an imagedisplay device such as a liquid crystal display (LCD) or an organicelectroluminescent (EL) display.

BACKGROUND ART

The image forming system of liquid crystal display devices haspolarizing films placed as essential components on both sides of glasssubstrates that form the liquid crystal panel surfaces. A polarizingfilm generally used includes a polarizer and a transparent protectivefilm or films bonded to one or both surfaces of the polarizer with apolyvinyl alcohol-based adhesive or any other adhesive, in which thepolarizer includes a polyvinyl alcohol-based film and a dichroicmaterial such as iodine.

In general, a pressure-sensitive adhesive is used to bond such apolarizing film to a liquid crystal cell or any other component. Thepressure-sensitive adhesive is provided as a pressure-sensitive adhesivelayer in advance on one surface of the polarizing film because such apressure-sensitive adhesive layer has advantages such as the ability toinstantly fix the polarizing film and no need to perform a drying stepfor fixing the polarizing film. Thus, apressure-sensitive-adhesive-layer-attached polarizing film is generallyused when a polarizing film is bonded.

Polarizing films and pressure-sensitive-adhesive-layer-attachedpolarizing films have a problem in that in a harsh environmentaccompanied by thermal shock (e.g., a heat shock test in which −30° C.and 80° C. temperature conditions are repeated, or a test at a hightemperature of 100° C.), the polarizer undergoes changes in shrinkagestress, so that cracks (through cracks) can easily occur entirely in thedirection of the absorption axis of the polarizer. In other words,pressure-sensitive-adhesive-layer-attached polarizing films haveinsufficient durability to thermal shock in the harsh environmentmentioned above. For thickness reduction, apressure-sensitive-adhesive-layer-attached polarizing film can beproduced using a one-side-protected polarizing film including apolarizer and a transparent protective film provided on only one surfaceof the polarizer. Particularly, such apressure-sensitive-adhesive-layer-attached polarizing film hasinsufficient durability to the thermal shock mentioned above. Inaddition, the thermal shock-induced through cracks become more likely tooccur as the size of the polarizing film increases.

In order to suppress the occurrence of the through cracks, for example,it is proposed to provide a pressure-sensitive-adhesive-layer-attachedpolarizing film including a one-side-protected polarizing film, aprotective layer provided on the polarizing film and having a tensileelastic modulus of 100 MPa or more, and a pressure-sensitive adhesivelayer provided on the protective layer (Patent Document 1). It is alsoproposed to provide a pressure-sensitive-adhesive-layer-attachedpolarizing film including a polarizer with a thickness of 25 μm or less,a protective layer provided on one surface of the polarizer andincluding a product obtained by curing a curable resin composition, atransparent protective film provided on the other surface of thepolarizer, and a pressure-sensitive adhesive layer provided on the outerside of the protective layer (Patent Document 2). Thepressure-sensitive-adhesive-layer-attached polarizing films described inPatent Documents 1 and 2 are effective in terms of suppressing theoccurrence of through cracks. In addition, polarizers have also beenreduced in thickness. For example, it is proposed to provide a thinpolarizer having controlled optical properties including a controlledsingle-body transmittance and a controlled degree of polarization andalso having high orientation (Patent Document 3).

PRIOR ART DOCUMENTS Patent Documents

-   Patent Document 1: JP-A-2010-009027-   Patent Document 2: JP-A-2013-160775-   Patent Document 3: JP-B1-4751481

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

Patent Documents 1 and 2 disclose that a reduction in thickness isachieved by using a one-side-protected polarizing film having atransparent protective film on only one surface of a polarizer, while aprotective layer is provided to suppress the occurrence of throughcracks in the direction of the absorption axis of the polarizer, whichwould otherwise be caused by the use of the one-side-protectedpolarizing film.

On the other hand, polarizers have also been reduced in thickness. Whena thinner polarizer (e.g., 10 μm or less in thickness) is used to form apolarizing film or a pressure-sensitive-adhesive-layer-attachedpolarizing film, changes in shrinkage stress in the polarizer becomesmaller. Therefore, it has been found that the use of a thinnerpolarizer makes it possible to suppress the occurrence of throughcracks.

However, it has been found that even through the occurrence of throughcracks is suppressed in a one-side-protected polarizing film or apressure-sensitive-adhesive-layer-attached polarizing film producedtherewith, extremely-fine partial cracks (hereafter also referred to asnano-slits) can occur in the absorption axis direction of the polarizerwhen the optical properties are controlled and the polarizer used isthin (e.g., 10 μm or less in thickness) as described in Patent Document3, and mechanical shock is applied to the one-side-protected polarizingfilm or the pressure-sensitive-adhesive-layer-attached polarizing filmproduced therewith (including a case where a load is applied to thepolarizer side by downward bending). It has also been found that thenano-slits can occur regardless of the polarizing film size. It has alsobeen found that the nano-slits do not occur when a double-side-protectedpolarizing film is used, which includes a polarizer and transparentprotective films on both surfaces of the polarizer. It has also beenfound that when a through crack occurs in a polarizer, any other throughcrack will not occur adjacent to the through crack because the stressaround the through crack is released, and that in contrast, not only anano-slit can occur alone but also nano-slits can occur adjacent to eachother. It has also been found that a through crack once formed in apolarizer has the ability to progressively extend in the absorption axisdirection of the polarizer, and that in contrast, nano-slits have noability to progressively extend. Thus, it has been found that thenano-slit is a new problem that occurs when a thin polarizer withoptical properties controlled within specific ranges is used to form aone-side-protected polarizing film in which the occurrence of throughcracks is suppressed, and that the nano-slit is a problem caused by aphenomenon different from that responsible for the through crack.

In addition, the nano-slits, which are extremely fine, cannot bedetected in a normal environment. Therefore, even if nano-slits occur ina polarizer, light leakage defects in the one-side-protected polarizingfilm or the pressure-sensitive-adhesive-layer-attached polarizing filmproduced therewith are difficult to find by only a glance. In otherwords, nano-slits are difficult to detect by automatic opticalinspection, which is generally used for defect inspection of aone-side-protected polarizing film being produced in the form of a longstrip. It has also been found that when one-side-protected polarizingfilms or pressure-sensitive-adhesive-layer-attached polarizing films arebonded to the glass substrates or other components of an image displaypanel and then placed in a heated environment, nano-slits can expand inthe widthwise direction, so that nano-slit-induced defects can bedetected (e.g., as the presence or absence of light leakage).

Thus, it is desired to suppress not only the occurrence of throughcracks but also the occurrence of nano-slits in a one-side-protectedpolarizing film having a polarizer with a thickness of 10 or less or ina pressure-sensitive-adhesive-layer-attached polarizing film producedwith such a one-side-protected polarizing film.

It is an object of the invention to provide a one-side-protectedpolarizing film that includes a polarizer and a transparent protectivefilm on only one surface of the polarizer and resists the occurrence ofthrough cracks and nano-slit-induced defects even when the polarizer hasspecific optical properties and a thickness of 10 μm or less. It isanother object of the invention to provide apressure-sensitive-adhesive-layer-attached polarizing film includingsuch a one-side-protected polarizing film and a pressure-sensitiveadhesive layer.

It is a further object of the invention to provide an image displaydevice having such a one-side-protected polarizing film or such apressure-sensitive-adhesive-layer-attached polarizing film and toprovide a method for continuously producing such an image displaydevice.

Means for Solving the Problems

As a result of intensive studies, the inventors have accomplished theinvention based on findings that the problems can be solved by theone-side-protected polarizing film, thepressure-sensitive-adhesive-layer-attached polarizing film, and othermeans described below.

That is, the present invention relates to a one-side-protectedpolarizing film, comprising:

a polarizer;

a transparent protective film provided on only one surface of thepolarizer; and

a transparent layer provided on another surface of the polarizer,wherein

the polarizer comprises a polyvinyl alcohol-based resin, has a thicknessof 10 μm or less, and is designed to have a single-body transmittance Tand a polarization degree P representing optical properties satisfyingthe condition of the following formula: P>−(10^(0.929T−42.4)−1)×100(provided that T<42.3) or P≥99.9 (provided that T≥42.3), and

the transparent layer has an 80° C. compressive elastic modulus of 0.1GPa or more.

In the one-side-protected polarizing film, the transparent layerpreferably is a product formed from a resin material.

In the one-side-protected polarizing film, the transparent layerpreferably has a thickness of less than 3 μm.

In the one-side-protected polarizing film, the polarizer preferablycontains 25% by weight or less of boric acid based on the total weightof the polarizer.

Further, the present invention relates to apressure-sensitive-adhesive-layer-attached polarizing film comprising:the one-side-protected polarizing film; and a pressure-sensitiveadhesive layer.

The pressure-sensitive-adhesive-layer-attached polarizing film may beused in such a form that the pressure-sensitive adhesive layer isprovided on the transparent layer of the one-side-protected polarizingfilm. Alternatively, the pressure-sensitive-adhesive-layer-attachedpolarizing film may be used in such a form that the pressure-sensitiveadhesive layer is provided on the transparent protective film of theone-side-protected polarizing film. A separator may also be provided onthe pressure-sensitive adhesive layer of thepressure-sensitive-adhesive-layer-attached polarizing film. Thepressure-sensitive-adhesive-layer-attached polarizing film provided withthe separator can be used in the form of a roll.

Further, the present invention relates to an image display devicecomprising the one-side-protected polarizing film or thepressure-sensitive-adhesive-layer-attached polarizing film.

Further, the present invention relates to a method for continuouslyproducing an image display device, the method comprising the steps of:

-   -   unwinding the pressure-sensitive-adhesive-layer-attached        polarizing film from the roll of the        pressure-sensitive-adhesive-layer-attached polarizing film;    -   feeding the pressure-sensitive-adhesive-layer-attached        polarizing film with the separator; and    -   continuously bonding the        pressure-sensitive-adhesive-layer-attached polarizing film to a        surface of an image display panel with the pressure-sensitive        adhesive layer interposed therebetween.

Further, the present invention relates to a method for continuouslyproducing an image display device, the method comprising the steps of:

-   -   unwinding the pressure-sensitive-adhesive-layer-attached        polarizing film from the roll of the        pressure-sensitive-adhesive-layer-attached polarizing film        according to claim 9;    -   feeding the pressure-sensitive-adhesive-layer-attached        polarizing film with the separator; and    -   continuously bonding the        pressure-sensitive-adhesive-layer-attached polarizing film to a        surface of an image display panel with the pressure-sensitive        adhesive layer interposed therebetween.

Effect of the Invention

The one-side-protected polarizing film and thepressure-sensitive-adhesive-layer-attached polarizing film of theinvention include a polarizer with a thickness of 10 μm or less and aremade thin. The thin polarizer with a thickness of 10 μm or less resiststhe occurrence of through cracks because changes in the shrinkage stressapplied to the polarizer by thermal shock are smaller in the thinpolarizer than in thick polarizers.

On the other hand, nano-slits are more likely to occur in thinpolarizers having specific optical properties. Nano-slits seem to occurwhen mechanical shock is applied to the one-side-protected polarizingfilm or the pressure-sensitive-adhesive-layer-attached polarizing filmproduced therewith, in the process of producing the one-side-protectedpolarizing film, in the process of producing thepressure-sensitive-adhesive-layer-attached polarizing film by forming apressure-sensitive adhesive layer on the one-side-protected polarizingfilm, or various processes after the production of thepressure-sensitive-adhesive-layer-attached polarizing film. Nano-slitsare assumed to be caused by a mechanism different from that responsiblefor through cracks caused by thermal shock. In addition, whenone-side-protected polarizing films orpressure-sensitive-adhesive-layer-attached polarizing films are bondedto the glass substrates or other components of an image display paneland then placed in a heated environment, nano-slits can expand in thewidthwise direction, so that nano-slit-induced defects can be detected(e.g., as the presence or absence of light leakage).

The one-side-protected polarizing film of the invention and thepressure-sensitive-adhesive-layer-attached polarizing film of theinvention have a transparent layer with an 80° C. compressive elasticmodulus of 0.1 GPa or more provided on the other surface of thepolarizer (the surface opposite to its surface on which the transparentprotective film is provided), which can suppress the occurrence ofdefects due to the expansion of nano-slits in the widthwise directioneven if the nano-slits occur in the polarizer of a one-side-protectedpolarizing film obtained before the formation of the transparent layer.

As described above, the one-side-protected polarizing film of theinvention and the pressure-sensitive-adhesive-layer-attached polarizingfilm produced therewith have a transparent layer (with an 80° C.compressive elastic modulus of 0.1 GPa or more) that makes it possibleto reduce the thickness to a satisfactory level and to allow thepolarizer to resist the occurrence of through crack-induced defects andnano-slit-induced defects.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of an example of theone-side-protected polarizing film of the invention.

FIGS. 2A and 2B are schematic cross-sectional views of examples of thepressure-sensitive-adhesive-layer-attached polarizing film of theinvention.

FIGS. 3A and 3B are exemplary schematic diagrams for a comparisonbetween a nano-slit and a through crack occurring in a polarizer.

FIGS. 4A to 4F are exemplary photographs of cross-sections ofone-side-protected polarizing films, which show the presence or absenceof a nano-slit and show that heating-induced expansion of a nano-slitdiffers depending on the presence or absence of a transparent layer.

FIGS. 5A and 5B are schematic views illustrating items to be evaluatedfor nano-slits in examples and comparative examples.

FIGS. 6A and 6B are exemplary photographs showing whether cracks arecaused by nano-slits, for the evaluation of examples and comparativeexamples.

FIG. 7 is an exemplary photograph showing progress of a through crackfor the evaluation of examples and comparative examples.

FIG. 8 is a schematic cross-sectional view of an example of a system forcontinuously producing image display devices.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the one-side-protected polarizing film 11 of the inventionand the pressure-sensitive-adhesive-layer-attached polarizing film 12 ofthe invention will be described with reference to FIGS. 1 and 2. Asillustrated in FIG. 1, a one-side-protected polarizing film 10 (withoutany transparent layer 3) includes, for example, a polarizer 1 and atransparent protective film 2 on only one surface of the polarizer 1.Although not shown, an intervening layer such as an adhesive layer, apressure-sensitive adhesive layer, or an undercoat layer (primer layer)is provided between the polarizer 1 and the transparent protective film2 stacked on each other. Although not shown, an adhesion facilitatinglayer or an activation treatment may be formed or performed on thetransparent protective film 2 of the one-side-protected polarizing film10, and the adhesion facilitating layer and an adhesive layer may bestacked on each other. As illustrated in FIG. 1, the one-side-protectedpolarizing film 11 of the invention (with a transparent layer 3)includes the one-side-protected polarizing film 10 and a transparentlayer 3 provided (directly) on one surface of the polarizer 1 (thesurface opposite to its surface on which the transparent protective film2 is provided).

As illustrated in FIGS. 2A and 2B, thepressure-sensitive-adhesive-layer-attached polarizing film 12 of theinvention includes the one-side-protected polarizing film 11 (with atransparent layer) and a pressure-sensitive adhesive layer 4. Thepressure-sensitive adhesive layer 4 may be provided on the transparentlayer 3 as illustrated in FIG. 2A or on the transparent protective film2 as illustrated in FIG. 2B. In addition, a separator 5 may be providedon the pressure-sensitive adhesive layer 4 of thepressure-sensitive-adhesive-layer-attached polarizing film 12 of theinvention, and a surface protective film 6 may be provided on theopposite side of the film 12 from the separator 5. FIGS. 2A and 2B showcases where the separator 5 and the surface protective film 6 are bothprovided on the pressure-sensitive-adhesive-layer-attached polarizingfilm 12. The pressure-sensitive-adhesive-layer-attached polarizing film12 provided with at least the separator 5 (and optionally furtherprovided with the surface protective film 6) may be used in the form ofa roll. As described below, for example, the roll is advantageously usedin a process that includes unwinding thepressure-sensitive-adhesive-layer-attached polarizing film 12 from theroll, feeding the film 12 on the separator 5, and bonding the film 12 tothe surface of an image display panel with the pressure-sensitiveadhesive layer 4 interposed therebetween (hereinafter, such a methodwill also be referred to as a “roll-to-panel process”, which istypically disclosed in JP-B1-4406043). Thepressure-sensitive-adhesive-layer-attached polarizing film preferablyhas the structure shown in FIG. 2A, for example, in order to suppresswarpage of the display panel after the bonding and to suppress theoccurrence of nano-slits. The surface protective film 6 may be providedon the one-side-protected polarizing film 10 and on theone-side-protected polarizing film 11 (with a transparent layer).

FIGS. 3A and 3B are schematic diagrams for comparing a nano-slit a and athrough crack b, which can occur in the polarizer. FIG. 3A showsnano-slits a occurring in the polarizer 1, and FIG. 3B shows a throughcrack b occurring in the polarizer 1. The nano-slits a are caused bymechanical shock and partially occur in the direction of the absorptionaxis of the polarizer 1. The nano-slits a cannot be observed at thebeginning of their formation, but become observable as they expand inthe widthwise direction in a hot environment (e.g., at 80° C. or 60° C.and 90% RH). On the other hand, the nano-slits a are not considered tohave the ability to progressively extend in the direction of theabsorption axis of the polarizer. In addition, the nano-slits a areconsidered to occur regardless of the size of the polarizing film. Notonly a single nano-slit a can occur alone, but also nano-slits a canoccur adjacent to one another. On the other hand, the through crack b iscaused by thermal shock (e.g., in a heat shock test). The through crackhas the ability to progressively extend in the direction of theabsorption axis of the polarizer, where the crack occurs. When a throughcrack b occurs, any other through crack will not occur adjacent theretobecause the stress around it is released.

FIGS. 4A to 4F are exemplary photographs of the cross-section of theone-side-protected polarizing film 10 or the transparent layer-attachedone-side-protected polarizing film 11 for showing the occurrence,expansion, and repair of a nano-slit a in the polarizer. FIG. 4A showsan example where no nano-slit occurs in a one-side-protected polarizingfilm 10 including a polarizer 1 and a transparent protective film 2 ononly one surface of the polarizer 1 with an adhesive layer 2 ainterposed therebetween. FIG. 4B shows an example where a nano-slit aoccurs in the one-side-protected polarizing film 10. FIGS. 4A and 4B areboth taken before heating. FIG. 4C is an exemplary photograph takenafter heating of the cross-section of the one-side-protected polarizingfilm 10 in which a nano-slit a occurs. FIG. 4C shows that due toheating, the nano-slit a expands in the polarizer 1. On the other hand,FIG. 4D is an exemplary photograph of the cross-section of a transparentlayer-attached one-side-protected polarizing film 11 obtained by forminga transparent layer 3 (with a thickness of 1 μm and an 80° C.compressive elastic modulus of 0.1 GPa or more) on theone-side-protected polarizing film 10 suffering from the nano-slit a.FIG. 4D shows that the nano-slit a in the polarizer 1 is repaired (a′)by the transparent layer 3. FIG. 4E is an exemplary photograph of thecross-section taken after heating of the transparent layer-attachedone-side-protected polarizing film 11 having the transparent layer 3(with a thickness of 1 μm and an 80° C. compressive elastic modulus of0.1 GPa or more). FIG. 4E shows that the repaired nano-slit (a′) doesnot expand after the heating. FIG. 4F is an exemplary photograph of thecross-section of another transparent layer-attached one-side-protectedpolarizing film 11′ obtained by forming another transparent layer 3′(with a thickness of 0.1 μm and an 80° C. compressive elastic modulus ofless than 0.1 GPa) on the one-side-protected polarizing film 10suffering from the nano-slit a. FIG. 4F shows that even though thetransparent layer 3′ is provided, the nano-slit a in the polarizer 1expands due to the heating because the transparent layer 3′ has a lowerelastic modulus. FIGS. 4A to 4F are each obtained by cutting thecross-section of a sample perpendicularly to the direction of theabsorption axis of the sample using a cross-section polisher or amicrotome and then observing the cross-section with a scanning electronmicroscope.

<Polarizer>

In the invention, the polarizer used has a thickness of 10 μm or less.In order to reduce the thickness and suppress the occurrence of throughcracks, the thickness of the polarizer is preferably 8 μm or less, morepreferably 7 μm or less, even more preferably 6 μm or less. On the otherhand, the thickness of the polarizer is preferably 2 μm or more, morepreferably 3 μm or more. The polarizer with such a small thickness isless uneven in thickness, has good visibility, and is lessdimensionally-variable and thus has high durability to thermal shock.

The polarizer used includes a polyvinyl alcohol-based resin. Forexample, the polarizer may be a product produced by a process includingadsorbing a dichroic material such as iodine or a dichroic dye to ahydrophilic polymer film such as a polyvinyl alcohol-based film, apartially-formalized polyvinyl alcohol-based film, or apartially-saponified, ethylene-vinyl acetate copolymer-based film anduniaxially stretching the film, or may be a polyene-based oriented filmsuch as a film of a dehydration product of polyvinyl alcohol or adehydrochlorination product of polyvinyl chloride. Among thesepolarizers, a polarizer including a polyvinyl alcohol-based film and adichroic material such as iodine is preferred.

For example, a polarizer including a uniaxially-stretched polyvinylalcohol-based film dyed with iodine can be produced by a processincluding immersing a polyvinyl alcohol film in an aqueous iodinesolution to dye the film and stretching the film to 3 to 7 times theoriginal length. If necessary, the film may also be immersed in anaqueous solution of potassium iodide or the like optionally containingboric acid, zinc sulfate, zinc chloride, or other materials. Ifnecessary, the polyvinyl alcohol-based film may be further immersed inwater for washing before it is dyed. If the polyvinyl alcohol-based filmis washed with water, dirt and any anti-blocking agent can be cleanedfrom the surface of the polyvinyl alcohol-based film, and the polyvinylalcohol-based film can also be allowed to swell so that unevenness suchas uneven dyeing can be effectively prevented. The film may be stretchedbefore, while, or after it is dyed with iodine. The film may also bestretched in an aqueous solution of boric acid, potassium iodide, or thelike or in a water bath.

In view of stretching stability and optical durability, the polarizerpreferably contains boric acid. In order to suppress the occurrence andexpansion of through cracks and nano-slits, the content of boric acid inthe polarizer is preferably 25% by weight or less, more preferably 20%by weight or less, even more preferably 18% by weight or less, furthermore preferably 16% by weight or less, based on the total weight of thepolarizer. If the content of boric acid in the polarizer is more than20% by weight, shrinkage stress in the polarizer can increase to makethrough cracks more likely to occur even when the thickness of thepolarizer is controlled to 10 μm or less, which is not preferred. On theother hand, in view of the stretching stability and optical durabilityof the polarizer, the boron content is preferably 10% by weight or more,more preferably 12% by weight or more, based on the total weight of thepolarizer.

Typical examples of the thin polarizer include the thin polarizersdescribed in, for example, JP-B1-4751486, JP-B1-4751481, JP-B1-4815544,JP-B1-5048120, WO 2014/077599 A, and WO 2014/077636 A or thin polarizersobtained by the production methods described in these publications.

The polarizer is designed to have a single-body transmittance T and apolarization degree P that represent optical properties satisfying thecondition of the following formula: P>−(10^(0.929T−42.4)−1)×100(provided that T<42.3) or P≥99.9 (provided that T≥42.3). The polarizerdesigned to satisfy the condition uniquely has the performance requiredfor a liquid crystal television display having a large display element.Specifically, such a display is required to have a contrast ratio of1,000:1 or more and a maximum brightness of 500 cd/m or more. In otherapplications, for example, the polarizer is bonded to the viewer side ofan organic EL display device.

On the other hand, the polarizer designed to satisfy the conditionincludes a polymer (e.g., a polyvinyl alcohol-based molecule) havinghigh orientation, which causes, together with the thickness of 10 μm orless, a significant reduction in the tensile rupture stress in thedirection perpendicular to the absorption axis direction of thepolarizer. This increases extremely the possibility that nano-slits mayoccur in the direction of the absorption axis of the polarizer, forexample, when the polarizer is exposed to mechanical shock beyond thetensile rupture stress in the process of producing the polarizing film.Therefore, the invention is particularly suitable for providing aone-side-protected polarizing film including the polarizer describedabove (or providing a pressure-sensitive-adhesive-layer-attachedpolarizing film including the polarizer described above).

The thin polarizer described above should be produced by a processcapable of achieving high-ratio stretching to improve polarizingperformance, among processes including the steps of stretching anddyeing a laminate. From this point of view, the thin polarizer ispreferably obtained by a process including the step of stretching in anaqueous boric acid solution as described in JP-B1-4751486,JP-B1-4751481, or JP-B1-4815544, and more preferably obtained by aprocess including the step of performing auxiliary in-air stretchingbefore stretching in an aqueous boric acid solution as described inJP-B1-4751481 or JP-B1-4815544. These thin polarizers can be obtained bya process including the steps of stretching a laminate of a polyvinylalcohol-based resin (hereinafter also referred to as PVA-based resin)layer and a stretchable resin substrate and dyeing the laminate. Usingthis process, the PVA-based resin layer, even when thin, can bestretched without problems such as breakage by stretching, because thelayer is supported on the stretchable resin substrate.

<Transparent Protective Film>

The transparent protective film is preferably made of a material havinga high level of transparency, mechanical strength, thermal stability,water barrier properties, isotropy, and other properties. Examples ofsuch a material include polyester-based polymers such as polyethyleneterephthalate and polyethylene naphthalate, cellulose-based polymerssuch as diacetyl cellulose and triacetyl cellulose, acryl-based polymerssuch as polymethyl methacrylate, styrene-based polymers such aspolystyrene and acrylonitrile-styrene copolymers (AS resins), andpolycarbonate polymers. Examples of polymers that may be used to formthe transparent protective film also include polyolefin-based polymerssuch as polyethylene, polypropylene, cyclo-based ornorbornene-structure-containing polyolefin, and ethylene-propylenecopolymers, vinyl chloride-based polymers, amide-based polymers such asnylon and aromatic polyamide, imide-based polymers, sulfone-basedpolymers, polyether sulfone-based polymers, polyether ether ketone-basedpolymers, polyphenylene sulfide-based polymers, vinyl alcohol-basedpolymers, vinylidene chloride-based polymers, vinyl butyral-basedpolymers, arylate-based polymers, polyoxymethylene-based polymers,epoxy-based polymers, or any blends of the above polymers.

The transparent protective film may also contain any type of one or moreappropriate additives. Examples of such additives include ultravioletabsorbers, antioxidants, lubricants, plasticizers, release agents,discoloration preventing agents, flame retardants, nucleating agents,antistatic agents, pigments, and colorants. The content of thethermoplastic resin in the transparent protective film is preferablyfrom 50 to 100% by weight, more preferably from 50 to 99% by weight,even more preferably from 60 to 98% by weight, further more preferablyfrom 70 to 97% by weight. If the content of the thermoplastic resin inthe transparent protective film is 50% by weight or less, hightransparency and other properties inherent in the thermoplastic resinmay fail to be sufficiently exhibited.

The transparent protective film may also be, for example, a retardationfilm, a brightness enhancement film, or a diffusion film. Theretardation film may have an in-plane retardation of 40 nm or moreand/or a thickness direction retardation of 80 nm or more. The in-planeretardation is generally adjusted to fall within the range of 40 to 200nm, and the thickness direction retardation is generally adjusted tofall within the range of 80 to 300 nm. When a retardation film is usedas the transparent protective film, the retardation film can also serveas a polarizer protecting film, which contributes to thicknessreduction.

The retardation film may be a birefringent film formed by subjecting athermoplastic resin film to uniaxial or biaxial stretching. Thestretching temperature, the stretch ratio, and other conditions may beappropriately selected depending on the retardation value, the filmmaterial, and the thickness.

The thickness of the transparent protective film may be selected asneeded. In general, the thickness of the transparent protective film isfrom about 1 to about 500 μm in view of strength, workability such ashandleability, and thin layer formability. In particular, the thicknessof the transparent protective film is preferably from 1 to 300 μm, morepreferably from 5 to 200 μm, even more preferably from 5 to 150 μm,further more preferably from 20 to 100 μm for thickness reduction.

The surface of the transparent protective film, opposite to its surfacewhere the polarizer is bonded (particularly in the mode shown in FIG.1), may be provided with a functional layer such as a hard coat layer,an anti-reflection layer, an anti-sticking layer, a diffusion layer, oran antiglare layer.

The functional layer such as a hard coat layer, an anti-reflectionlayer, an anti-sticking layer, a diffusion layer, or an antiglare layermay be provided as part of the transparent protective film itself or asa layer independent of the transparent protective film.

<Intervening Layer>

The transparent protective film and the polarizer are laminated with anintervening layer, such as an adhesive layer, a pressure-sensitiveadhesive layer, or an undercoat layer (primer layer), between them. Inthis case, the intervening layer should preferably be used to laminatethem with no air gap between them.

The adhesive layer is made from an adhesive. Any of various types ofadhesives may be used. The adhesive layer may be of anyoptically-transparent type. The adhesive may be any of various types,such as a water-based adhesive, a solvent-based adhesive, a hotmelt-based adhesive, and an active energy ray-curable adhesive. Awater-based adhesive or an active energy ray-curable adhesive ispreferred.

The water-based adhesive may be, for example, an isocyanate-basedadhesive, a polyvinyl alcohol-based adhesive, a gelatin-based adhesive,a vinyl-based adhesive, a latex-based adhesive, or a water-basedpolyester adhesive. The water-based adhesive is generally used in theform of an aqueous solution, which generally has a solids content of 0.5to 60% by weight.

The active energy ray-curable adhesive is an adhesive capable of beingcured by exposure to active energy rays such as electron beams orultraviolet rays (a radically or cationically curable adhesive). Theactive energy ray-curable adhesive to be used may be of, for example, anelectron beam-curable type or an ultraviolet-curable type. The activeenergy ray-curable adhesive may be, for example, a photo-radicallycurable adhesive. The photo-radically curable type active energyray-curable adhesive may be of an ultraviolet-curable type. In thiscase, the adhesive should contain a radically polymerizable compound anda photopolymerization initiator.

The method for applying the adhesive is appropriately selected dependingon the viscosity of the adhesive and the desired thickness. Examples ofapplication means include a reverse coater, a gravure coater (direct,reverse, or offset), a bar reverse coater, a roll coater, a die coater,a bar coater, and a rod coater. Any other suitable application methodsuch as dipping may also be used.

For example, when the water-based adhesive is used, the adhesive ispreferably applied in such a manner that the finally formed adhesivelayer can have a thickness of 30 to 300 nm. The adhesive layer morepreferably has a thickness of 60 to 250 nm. On the other hand, when theactive energy ray-curable adhesive is used, the adhesive layer ispreferably formed with a thickness of 0.1 to 200 μm. The thickness ismore preferably from 0.5 to 50 μm, even more preferably from 0.5 to 10μm.

In the process of laminating the polarizer and the transparentprotective film, an adhesion-facilitating layer may be placed betweenthe transparent protective film and the adhesive layer. Theadhesion-facilitating layer may be made of, for example, any of variousresins having a polyester skeleton, a polyether skeleton, apolycarbonate skeleton, a polyurethane skeleton, a silicone skeleton, apolyamide skeleton, a polyimide skeleton, a polyvinyl alcohol skeleton,or other polymer skeletons. These polymer resins may be used singly orin combination of two or more. Other additives may also be added to formthe adhesion-facilitating layer. More specifically, a tackifier, anultraviolet absorber, an antioxidant, or a stabilizer such as aheat-resistant stabilizer may also be used to form theadhesion-facilitating layer.

The adhesion-facilitating layer is usually provided in advance on thetransparent protective film, and then the adhesion-facilitating layerside of the transparent protective film is bonded to the polarizer withthe adhesive layer. The adhesion-facilitating layer can be formed usinga known technique that includes applying anadhesion-facilitating-layer-forming material onto the transparentprotective film and drying the material. Theadhesion-facilitating-layer-forming material is generally prepared inthe form of a solution which is diluted to a suitable concentrationtaking into account the coating thickness after drying, the smoothnessof the application, and other factors. After dried, theadhesion-facilitating layer preferably has a thickness of 0.01 to 5 μm,more preferably 0.02 to 2 μm, even more preferably 0.05 to 1 μm. Two ormore adhesion-facilitating layers may be provided. Also in this case,the total thickness of the adhesion-facilitating layers preferably fallswithin these ranges.

The pressure-sensitive adhesive layer is made from a pressure-sensitiveadhesive. Any of various pressure-sensitive adhesives may be used,examples of which include rubber-based pressure-sensitive adhesives,acryl-based pressure-sensitive adhesives, silicone-basedpressure-sensitive adhesives, polyurethane-based pressure-sensitiveadhesives, vinyl alkyl ether-based pressure-sensitive adhesives,polyvinylpyrrolidone-based pressure-sensitive adhesives,polyacrylamide-based pressure-sensitive adhesives, and cellulose-basedpressure-sensitive adhesives. The base polymer with adhesive propertiesis selected depending on the type of the pressure-sensitive adhesive.Among these pressure-sensitive adhesive adhesives, acryl-basedpressure-sensitive adhesives are preferably used because they have ahigh level of optical transparency, weather resistance, heat resistance,and other properties, and exhibit an appropriate level of wettabilityand adhesive properties including cohesiveness and adhesiveness.

The undercoat layer (primer layer) is formed to improve the adhesionbetween the polarizer and the protective film. The primer layer may bemade of any material capable of providing somewhat strong adhesion toboth the base film and a polyvinyl alcohol-based resin layer. Forexample, a thermoplastic resin having a high level of transparency,thermal stability, and stretchability may be used to form the primerlayer. Such a thermoplastic resin may be, for example, an acryl-basedresin, a polyolefin-based resin, a polyester-based resin, a polyvinylalcohol-based resin, or any mixture thereof.

<Transparent Layer>

In the one-side-protected polarizing film having the transparentprotective film provided on only one surface of the polarizer, thetransparent layer is provided on the other surface of the polarizer (thesurface opposite to its surface on which the transparent protective filmis placed). In the invention, the transparent layer has an 80° C.compressive elastic modulus of 0.1 GPa or more. Even if nano-slits occurin the polarizer due to mechanical shock and are capable of expanding inthe widthwise direction in a hot environment, the transparent layer witha controlled 80° C. compressive elastic modulus of 0.1 GPa or more canmaintain the ability to withstand mechanical loads even in a hotenvironment and thus can suppress the expansion of the nano-slits in thewidthwise direction. The compressive elastic modulus of the transparentlayer is preferably 0.5 GPa or more, more preferably 2 GPa or more, evenmore preferably 5 GPa or more, further more preferably 10 GPa or more.The compressive elastic modulus of the transparent layer can becontrolled by selecting the material. In this regard, the 80° C.compressive elastic modulus C of the transparent layer is the valuemeasured by the method described in the EXAMPLES section.

In view of thickness reduction and optical reliability, the transparentlayer preferably has a thickness of less than 3 μm, more preferably 2 μmor less, even more preferably 1.5 pun or less, further more preferably 1μm or less. On the other hand, in view of the effect of suppressing theexpansion of nano-slits, the transparent layer preferably has athickness of 0.2 μm or more, more preferably 0.6 μm or more, even morepreferably 0.8 μm or more.

The transparent layer can be formed from any of various layer-formingmaterials. The transparent layer can be formed by, for example, applyinga resin material to the polarizer or vapor-depositing an inorganic oxidesuch as SiO₂ on the polarizer by sputtering or other methods. Thetransparent layer is preferably formed from a resin material so that itcan be easily formed.

The transparent layer may be formed from a curable, layer-formingmaterial containing a curable component (may be a product obtained bycuring a curable, layer-forming material). The curable component can bebroadly classified into an active energy ray-curable type such as anelectron beam-curable type, an ultraviolet-curable type, or a visiblelight-curable type; and a thermosetting type. The ultraviolet-curabletype and the visible light-curable type can be further classified into aradically polymerizable curable type and a cationically polymerizablecurable type. In the invention, active energy rays in the wavelengthrange of 10 nm to less than 380 nm are called ultraviolet rays orultraviolet light, and active energy rays in the wavelength range of 380nm to 800 nm are called visible rays or visible light. The curablecomponent of the radically polymerizable curable material can be used asa thermosetting curable component.

<<Radically Polymerizable, Curable, Layer-Forming Material>>

Examples of the curable component include radically polymerizablecompounds. Radically polymerizable compounds include compounds having aradically-polymerizable carbon-carbon double bond-containing functionalgroup, such as a (meth)acryloyl group or a vinyl group. The curablecomponent may be any of a monofunctional radically polymerizablecompound or a bifunctional or polyfunctional radically polymerizablecompound. These radically polymerizable compounds may be used singly orin combination of two or more. These radically polymerizable compoundsare preferably, for example, (meth)acryloyl group-containing compounds.In the invention, the term “(meth)acryloyl” means acryloyl and/ormethacryloyl, and hereinafter, “(meth)” is used in the same meaning.

<<Monofunctional Radically Polymerizable Compound>>

The monofunctional radically polymerizable compound may be, for example,a (meth)acrylamide derivative having a (meth)acrylamide group. The(meth)acrylamide derivative is preferable in order to ensure theadhesion to the polarizer and in terms of having high polymerizationrate and providing high productivity. Examples of the (meth)acrylamidederivative include N-alkyl group-containing (meth)acrylamide derivativessuch as N-methyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide,N,N-diethyl(meth)acrylamide, N-isopropyl(meth)acrylamide,N-butyl(meth)acrylamide, and N-hexyl(meth)acrylamide; N-hydroxyalkylgroup-containing (meth)acrylamide derivatives such asN-methylol(meth)acrylamide, N-hydroxyethyl(meth)acrylamide, andN-methylol-N-propane(meth)acrylamide; N-aminoalkyl group-containing(meth)acrylamide derivatives such as aminomethyl(meth)acrylamide andaminoethyl(meth)acrylamide; N-alkoxy group-containing (meth)acrylamidederivatives such as N-methoxymethylacrylamide andN-ethoxymethylacrylamide; and N-mercaptoalkyl group-containing(meth)acrylamide derivatives such as mercaptomethyl(meth)acrylamide andmercaptoethyl(meth)acrylamide. Heterocyclic ring-containing(meth)acrylamide derivatives in which the nitrogen atom of a(meth)acrylamide group forms a heterocyclic ring may also be used, suchas N-acryloylmorpholine, N-acryloylpiperidine, N-methacryloylpiperidine,and N-acryloylpyrrolidine.

Among the (meth)acrylamide derivatives, N-hydroxyalkyl group-containing(meth)acrylamide derivatives are preferred in view of adhesion to thepolarizer, and N-hydroxyethyl(meth)acrylamide is particularly preferred.

Examples of the monofunctional radically polymerizable compound alsoinclude various (meth)acrylic acid derivatives having a(meth)acryloyloxy group. Specific examples include (C1 to C20) alkyl(meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate,n-propyl (meth)acrylate, isopropyl (meth)acrylate,2-methyl-2-nitropropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl(meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate,n-pentyl (meth)acrylate, tert-pentyl (meth)acrylate, 3-pentyl(meth)acrylate, 2,2-dimethylbutyl (meth)acrylate, n-hexyl(meth)acrylate, cetyl (meth)acrylate, n-octyl (meth)acrylate,2-ethylhexyl (meth)acrylate, 4-methyl-2-propylpentyl (meth)acrylate, andn-octadecyl (meth)acrylate.

Examples of the (meth)acrylic acid derivatives also include cycloalkyl(meth)acrylates such as cyclohexyl (meth)acrylate and cyclopentyl(meth)acrylate; aralkyl (meth)acrylates such as benzyl (meth)acrylate;polycyclic (meth)acrylates such as 2-isobornyl (meth)acrylate,2-norbornylmethyl (meth)acrylate, 5-norbornen-2-yl-methyl(meth)acrylate, 3-methyl-2-norbornylmethyl (meth)acrylate,dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylateand dicyclopentanyl (meth)acrylate; and alkoxy group- or phenoxygroup-containing (meth)acrylates such as 2-methoxyethyl (meth)acrylate,2-ethoxyethyl (meth)acrylate, 2-methoxymethoxyethyl (meth)acrylate,3-methoxybutyl (meth)acrylate, ethylcarbitol (meth)acrylate,phenoxyethyl (meth)acrylate, and alkylphenoxy polyethylene glycol(meth)acrylate.

Examples of the (meth)acrylic acid derivatives also include hydroxyalkyl(meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl(meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl(meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl(meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl(meth)acrylate, and 12-hydroxylauryl (meth)acrylate, and other hydroxygroup-containing (meth)acrylates such as[4-(hydroxymethyl)cyclohexyl]methyl acrylate, cyclohexanedimethanolmono(meth)acrylate, and 2-hydroxy-3-phenoxypropyl (meth)acylate; epoxygroup-containing (meth)acrylates such as glycidyl (meth)acrylate and4-hydroxybutyl (meth)acrylate glycidyl ether; halogen-containing(meth)acrylates such as 2,2,2-trifluoroethyl (meth)acrylate,2,2,2-trifluoroethylethyl (meth)acrylate, tetrafluoropropyl(meth)acrylate, hexafluoropropyl (meth)acrylate, octafluoropentyl(meth)acrylate, heptadecafluorodecyl (meth)acrylate, and3-chloro-2-hydroxypropyl (meth)acrylate; alkylaminoalkyl (meth)acrylatessuch as dimethylaminoethyl (meth)acrylate; oxetane group-containing(meth)acrylates such as 3-oxetanylmethyl (meth)acrylate,3-methyl-oxetanylmethyl (meth)acrylate, 3-ethyl-oxetanylmethyl(meth)acrylate, 3-butyl-oxetanylmethyl (meth)acrylate, and3-hexyl-oxetanylmethyl (meth)acrylate; heterocyclic ring-containing(meth)acrylates such as tetrahydrofurfuryl (meth)acrylate andbutyrolactone (meth)acrylate; and (meth)acrylic acid adducts ofneopentyl glycol hydroxypivalate, and p-phenylphenol (meth)acrylate.

Examples of the monofunctional radically polymerizable compound alsoinclude carboxyl group-containing monomers such as (meth)acrylic acid,carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleicacid, fumaric acid, crotonic acid, and isocrotonic acid.

Examples of the monofunctional radically polymerizable compound alsoinclude vinyl lactam monomers such as N-vinylpyrrolidone,N-vinyl-ε-caprolactam, and methylvinylpyrrolidone; and vinyl monomershaving a nitrogen-containing heterocyclic ring, such as vinylpyridine,vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine,vinylpyrrole, vinylimidazole, vinyloxazole, and vinylmorpholine.

The monofunctional radically polymerizable compound may also be aradically polymerizable compound having an active methylene group. Theradically polymerizable compound having an active methylene group shouldbe a compound having an active double-bond group such as a (meth)acrylicgroup at its end or in its molecule and also having an active methylenegroup. The active methylene group may be, for example, an acetoacetylgroup, an alkoxymalonyl group, or a cyanoacetyl group. The activemethylene group is preferably an acetoacetyl group. Examples of theradically polymerizable compound having an active methylene groupinclude acetoacetoxyalkyl (meth)acrylates such as 2-acetoacetoxyethyl(meth)acrylate, 2-acetoacetoxypropyl (meth)acrylate, and2-acetoacetoxy-1-methylethyl (meth)acrylate; 2-ethoxymalonyloxyethyl(meth)acrylate, 2-cyanoacetoxyethyl (meth)acrylate,N-(2-cyanoacetoxyethyl)acrylamide,N-(2-propionylacetoxybutyl)acrylamide,N-(4-acetoacetoxymethylbenzyl)acrylamide, andN-(2-acetoacetylaminoethyl)acrylamide. The radically polymerizablecompound having an active methylene group is preferablyacetoacetoxyalkyl (meth)acrylate.

<<Polyfunctional Radically Polymerizable Compound>>

Examples of the bifunctional or polyfunctional radically polymerizablecompound include tripropylene glycol di(meth)acrylate, tetraethyleneglycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanedioldi(meth)acrylate, 1,10-decanediol diacrylate, 2-ethyl-2-butylpropanedioldi(meth)acrylate, bisphenol A di(meth)acrylate, bisphenol A ethyleneoxide adduct di(meth)acrylate, bisphenol A propylene oxide adductdi(meth)acrylate, bisphenol A diglycidyl ether di(meth)acrylate,neopentyl glycol di(meth)acrylate, tricyclodecanedimethanoldi(meth)acrylate, cyclic trimethylolpropane formal (meth)acrylate,dioxaneglycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate,pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate,dipentaerythritol penta(meth)acrylate, dipentaerythritolhexa(meth)acrylate, polyhydric alcohol esters of (meth)acrylic acid,such as EO-modified diglycerin tetra(meth)acrylate, and9,9-bis[4-(2-(meth)acryloyloxyethoxy)phenyl]fluorene. Specific examplesinclude Aronix M-220 and Aronix M-306 (manufactured by Toagosei Co.,Ltd.), LIGHT ACRYLATE 1,9ND-A (manufactured by Kyoeisha Chemical Co.,Ltd.), LIGHT ACRYLATE DGE-4A (manufactured by Kyoeisha Chemical Co.,Ltd.), LIGHT ACRYLATE DCP-A (manufactured by Kyoeisha Chemical Co.,Ltd.), SR-531 (manufactured by Sartomer), and CD-536 (manufactured bySartomer). If necessary, various epoxy (meth)acrylates, urethane(meth)acrylates, polyester (meth)acrylates, or various(meth)acrylate-based monomers may also be used.

In order to achieve both good adhesion to the polarizer and good opticaldurability, the monofunctional radically polymerizable compound ispreferably used in combination with the polyfunctional radicallypolymerizable compound. In general, 3 to 80% by weight of themonofunctional radically polymerizable compound is preferably used incombination with 20 to 97% by weight of the polyfunctional radiallypolymerizable compound based on 100% by weight of the radicallypolymerizable compounds.

<<Mode of Radically Polymerizable, Curable, Layer-Forming Material>>

The radically polymerizable, curable, layer-forming material to be usedmay be an active energy ray-curable, layer-forming material or athermosetting, layer-forming material. When an electron beam is used asthe active energy ray, the active energy ray-curable, layer-formingmaterial does not have to contain a photopolymerization initiator, butwhen an ultraviolet or visible ray is used as the active energy ray, theactive energy ray-curable, layer-forming material should preferablycontain a photopolymerization initiator. On the other hand, when thecurable component is used as a thermosetting component, thelayer-forming material should preferably contain a thermalpolymerization initiator.

<<Photopolymerization Initiator>>

The photopolymerization initiator for use with the radicallypolymerizable compound is appropriately selected depending on the typeof the active energy ray. For curing with ultraviolet or visible light,an ultraviolet or visible light-cleavable photopolymerization initiatorshould be used. Examples of the photopolymerization initiator includebenzophenone-based compounds such as benzil, benzophenone,benzoylbenzoic acid, and 3,3′-dimethyl-4-methoxybenzophenone; aromaticketone compounds such as4-(2-hydroxyethoxy)phenyl(2-hydroxy-2-propyl)ketone,α-hydroxy-α,α′-dimethylacetophenone, 2-methyl-2-hydroxypropiophenone,and α-hydroxycyclohexyl phenyl ketone; acetophenone-based compounds suchas methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone,2,2-diethoxyacetophenone, and2-methyl-1-[4-(methylthio)-phenyl]-2-morpholinopropane-1; benzoinether-based compounds such as benzoin methyl ether, benzoin ethyl ether,benzoin isopropyl ether, benzoin butyl ether, and anisoin methyl ether;aromatic ketal-based compounds such as benzyl dimethyl ketal; aromaticsulfonyl chloride-based compounds such as 2-naphthalenesulfonylchloride; optically active oxime-based compounds such asl-phenone-1,1-propanedione-2-(o-ethoxycarbonyl)oxime; thioxanthone-basedcompounds such as thioxanthone, 2-chlorothioxanthone,2-methyithioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone,2,4-dichlorothioxanthone, 2,4-diethyithioxanthone,2,4-diisopropylthioxanthone, and dodecylthioxanthone; camphorquinone;halogenated ketones; acylphosphine oxide; and acylphosphonate.

The content of the photopolymerization initiator should be 20 parts byweight or less based on 100 parts by weight of the total amount of thecurable components (radically polymerizable compounds). The content ofthe photopolymerization initiator is preferably from 0.01 to 20 parts byweight, more preferably from 0.05 to 10 parts by weight, even morepreferably from 0.1 to 5 parts by weight.

When the curable, layer-forming material used for the polarizing film ofthe invention is a visible light-curable, layer-forming materialcontaining the radically polymerizable compound as the curablecomponent, a photopolymerization initiator having high sensitivityparticularly to light of 380 nm or longer is preferably used in thelayer-forming material. The photopolymerization initiator having highsensitivity to light of 380 nm or longer will be described later.

A compound represented by formula (1):

wherein R¹ and R² each represent —H, —CH₂CH₃, -i-Pr, or Cl, and R¹ andR² may be the same or different, is preferably used alone as thephotopolymerization initiator or preferably used as thephotopolymerization initiator in combination with anotherphotopolymerization initiator having high sensitivity to light of 380 nmor longer described later. The resulting adhesion is higher when thecompound of formula (1) is used than when a photopolymerizationinitiator having high sensitivity to light of 380 nm or longer is usedalone. In particular, the compound of formula (1) is preferably diethylthioxanthone in which R¹ and R² are each —CH₂CH₃. The content of thecompound of formula (1) in the layer-forming material is preferably from0.1 to 5 parts by weight, more preferably from 0.5 to 4 parts by weight,even more preferably from 0.9 to 3 parts by weight, based on 100 partsby weight of the total amount of the curable components.

If necessary, a polymerization initiation aid is preferably added to thelayer-forming material. In particular, the polymerization initiation aidis preferably triethylamine, diethylamine, N-methyldiethanolamine,ethanolamine, 4-dimethylaminobenzoic acid, methyl4-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate, or isoamyl4-dimethylaminobenzoate. Ethyl 4-dimethylaminobenzoate is particularlypreferred. When the polymerization initiation aid is used, the contentof the aid is generally 0 to 5 parts by weight, preferably 0 to 4 partsby weight, most preferably 0 to 3 parts by weight, based on 100 parts byweight of the total amount of the curable components.

If necessary, a known photopolymerization initiator may be used incombination. Since the transparent protective film having the ability toabsorb UV does not transmit light of 380 nm or shorter, such aphotopolymerization initiator should preferably have high sensitivity tolight of 380 nm or longer. Examples of such an initiator include2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one,2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1,2-(dimethylamino)-2-[(4-methylphenyl)methyl]-[4-(4-morpholinyl)phenyl]-1-butanone,2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide,bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, andbis(η5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl)titanium.

In particular, a compound represented by formula (2):

wherein R³, R⁴, and R⁵ each represent —H, —CH₃, —CH₂CH₃, -i-Pr, or Cl,and R³, R⁴, and R⁵ may be the same or different, is preferably used inaddition to the photopolymerization initiator of formula (1).Commercially available2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one (IRGACURE 907(trade name) manufactured by BASF) is preferably used as the compound offormula (2). Besides this,2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1 (IRGACURE 369(trade name) manufactured by BASF) and2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone(IRGACURE 379 (trade name) manufactured by BASF) are preferred becauseof their high sensitivity.

<Radically Polymerizable Compound Having Active Methylene Group andRadical Polymerization Initiator Having Hydrogen-Withdrawing Function>

The radically polymerizable compound used in the active energyray-curable, layer-forming material may be a radically polymerizablecompound having an active methylene group. In this case, the radicallypolymerizable compound is preferably used in combination with a radicalpolymerization initiator having a hydrogen-withdrawing function.

The radical polymerization initiator having a hydrogen-withdrawingfunction may be, for example, a thioxanthone-based radicalpolymerization initiator or a benzophenone-based radical polymerizationinitiator. The radical polymerization initiator is preferably athioxanthone-based radical polymerization initiator. Thethioxanthone-based radical polymerization initiator may be, for example,the compound of formula (1) shown above. Examples of the compound offormula (1) include thioxanthone, dimethyl thioxanthone, diethylthioxanthone, isopropyl thioxanthone, and chlorothioxanthone. Inparticular, the compound of formula (1) is preferably diethylthioxanthone in which R¹ and R² are each —CH₂CH₃.

When the active energy ray-curable, layer-forming material contains theradically polymerizable compound having an active methylene group andthe radical polymerization initiator having a hydrogen-withdrawingfunction, the content of the radically polymerizable compound having anactive methylene group is preferably from 1 to 50% by weight based on100% by weight of the total amount of the curable components, and thecontent of the radical polymerization initiator is preferably from 0.1to 10 parts by weight based on 100 parts by weight of the total amountof the curable components.

<<Thermal Polymerization Initiator>>

The thermal polymerization initiator is preferably such that it does notstart undergoing thermal cleavage-induced polymerization when theadhesive layer is formed. For example, the thermal polymerizationinitiator preferably has a 10-hour half-life temperature of 65° C. ormore, more preferably 75 to 90° C. The term “half-life,” which is anindicator of how fast the polymerization initiator can be decomposed,refers to the time required for the remaining amount of thepolymerization initiator to reach one half of the original amount. Thedecomposition temperature required for a certain half-life time and thehalf-life time obtained at a certain temperature are shown in catalogsfurnished by manufacturers, such as Organic Peroxide Catalog, 9thEdition, May, 2003, furnished by NOF CORPORATION.

Examples of the thermal polymerization initiator include organicperoxides such as lauroyl peroxide (10-hour half-life temperature: 64°C.), benzoyl peroxide (10-hour half-life temperature: 73° C.),1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane (10-hour half-lifetemperature: 90° C.), di(2-ethylhexyl) peroxydicarbonate (10-hourhalf-life temperature: 49° C.), di(4-tert-butylcyclohexyl)peroxydicarbonate, di-sec-butyl peroxydicarbonate (10-hour half-lifetemperature: 51° C.), tert-butyl peroxyneodecanoate (10-hour half-lifetemperature: 48° C.), tert-hexyl peroxypivalate, tert-butylperoxypivalate, dilauroyl peroxide (10-hour half-life temperature: 64°C.), di-n-octanoyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate (10-hour half-life temperature: 66° C.), di(4-methylbenzoyl)peroxide, dibenzoyl peroxide (10-hour half-life temperature: 73° C.),tert-butyl peroxyisobutyrate (10-hour half-life temperature: 81° C.),and 1,1-di(tert-hexylperoxy)cyclohexane.

Examples of the thermal polymerization initiator also include azocompounds such as 2,2′-azobisisobutyronitrile (10-hour half-lifetemperature: 67° C.), 2,2′-azobis(2-methylbutyronitrile) (10-hourhalf-life temperature: 67° C.), and1,1-azobis-cyclohexane-1-carbonitrile (10-hour half-life temperature:87° C.).

The content of the thermal polymerization initiator may be from 0.01 to20 parts by weight based on 100 parts by weight of the total amount ofthe curable components (radically polymerizable compounds). The contentof the thermal polymerization initiator is preferably from 0.05 to 10parts by weight, more preferably from 0.1 to 3 parts by weight.

<<Cationically Polymerizable, Curable, Layer-Forming Material>>

The curable component of the cationically polymerizable, curable,layer-forming material may be an epoxy or oxetanyl group-containingcompound. The epoxy group-containing compound may be any compound havingat least two epoxy groups per molecule. A variety of generally knowncurable epoxy compounds may be used. Preferred epoxy compounds are, forexample, compounds having at least two epoxy groups and at least onearomatic ring per molecule (aromatic epoxy compounds) or compoundshaving at least two epoxy groups per molecule, in which at least one ofthem is formed between two adjacent carbon atoms that form an alicyclicring (alicyclic epoxy compounds).

<<Photo-Cationic Polymerization Initiator>>

The cationically polymerizable, curable, layer-forming material shouldcontain, as curable components, the epoxy compound and the oxetanecompound described above, which are both curable by cationicpolymerization. Therefore, the cationically polymerizable, curable,layer-forming material should contain a photo-cationic polymerizationinitiator. When irradiated with active energy rays such as visiblelight, ultraviolet light, X-rays, or electron beams, the photo-cationicpolymerization initiator can produce a cationic species or a Lewis acidto initiate the polymerization reaction of the epoxy or oxetanyl group.

<Other Components>

In the invention, the curable, layer-forming material preferablycontains the components described below.

<Acryl-Based Oligomer>

In the invention, the active energy ray-curable, layer-forming materialmay contain, in addition to the radically polymerizable compounds as thecurable components, an acryl-based oligomer obtained by polymerizationof a (meth)acrylic monomer. The acryl-based oligomer in the activeenergy ray-curable, layer-forming material can reduce curing-inducedshrinkage in the process of curing the transparent layer by applicationof active energy rays and can reduce the stress at the interface betweenthe transparent layer and the adherend such as the polarizer. As aresult, the acryl-based oligomer can suppress the reduction in theadhesion between the adhesive layer and the adherend. In order tosuppress curing-induced shrinkage sufficiently, the content of theacryl-based oligomer is preferably 20 parts by weight or less, morepreferably 15 parts by weight or less, based on 100 parts by weight ofthe total amount of the curable components. If the content of theacryl-based oligomer in the layer-forming material is too high, thereaction rate in the process of applying active energy rays to thelayer-forming material may sharply decrease, which may result ininsufficient curing. On the other hand, the content of the acryl-basedoligomer is preferably 3 parts by weight or more, more preferably 5parts by weight or more, based on 100 parts by weight of the totalamount of the curable components.

In view of workability and uniformity during application, the activeenergy ray-curable, layer-forming material should preferably have lowviscosity. Therefore, the acryl-based oligomer obtained bypolymerization of a (meth)acrylic monomer should also preferably havelow viscosity. In order to have low viscosity and the ability to preventthe curing-induced shrinkage of the transparent layer, the acryl-basedoligomer preferably has a weight average molecular weight (Mw) of 15,000or less, more preferably 10,000 or less, even more preferably 5,000 orless. On the other hand, in order to suppress the curing-inducedshrinkage of the transparent layer sufficiently, the acryl-basedoligomer preferably has a weight average molecular weight (Mw) of 500 ormore, more preferably 1,000 or more, even more preferably 1,500 or more.Examples of (meth)acrylic monomers that may be used to form theacryl-based oligomer include (C1 to C20) alkyl (meth)acrylates such asmethyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate,isopropyl (meth)acrylate, 2-methyl-2-nitropropyl (meth)acrylate, n-butyl(meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate,tert-butyl (meth)acrylate, n-pentyl (meth)acrylate, tert-pentyl(meth)acrylate, 3-pentyl (meth)acrylate, 2,2-dimethylbutyl(meth)acrylate, n-hexyl (meth)acrylate, cetyl (meth)acrylate, n-octyl(meth)acrylate, 2-ethylhexyl (meth)acrylate, 4-methyl-2-propylpentyl(meth)acrylate, and n-octadecyl (meth)acrylate; cycloalkyl(meth)acrylates (such as cyclohexyl (meth)acrylate and cyclopentyl(meth)acrylate); aralkyl (meth)acrylates (such as benzyl(meth)acrylate); polycyclic (meth)acrylates (such as 2-isobornyl(meth)acrylate, 2-norbornylmethyl (meth)acrylate,5-norbornen-2-yl-methyl (meth)acrylate, and 3-methyl-2-norbornylmethyl(meth)acrylate); hydroxyl group-containing (meth)acrylates (such ashydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and2,3-dihydroxypropylmethyl-butyl (meth)acrylate); alkoxy group- orphenoxy group-containing (meth)acrylates (such as 2-methoxyethyl(meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-methoxymethoxyethyl(meth)acrylate, 3-methoxybutyl (meth)acrylate, ethylcarbitol(meth)acrylate, and phenoxyethyl (meth)acrylate); epoxy group-containing(meth)acrylates (such as glycidyl (meth)acrylate); halogen-containing(meth)acrylates (such as 2,2,2-trifluoroethyl (meth)acrylate,2,2,2-trifluoroethylethyl (meth)acrylate, tetrafluoropropyl(meth)acrylate, hexafluoropropyl (meth)acrylate, octafluoropentyl(meth)acrylate, and heptadecafluorodecyl (meth)acrylate); andalkylaminoalkyl (meth)acrylates (such as dimethylaminoethyl(meth)acrylate). These (meth)acrylates may be used alone or incombination of two or more. Examples of the acryl-based oligomer includeARUFON manufactured by Toagosei Co., Ltd., Actflow manufactured by SokenChemical & Engineering Co., Ltd., and JONCRYL manufactured by BASF JapanLtd.

<Photo-Acid Generator>

The active energy ray-curable, layer-forming material may contain aphoto-acid generator. When the active energy ray-curable, layer-formingmaterial contains a photo-acid generator, the resulting transparentlayer can have a dramatically higher level of water resistance anddurability than that in the case where the layer-forming materialcontains no photo-acid generator. The photo-acid generator may berepresented by formula (3) below.

Formula (3):L⁺X⁻  [Formula. 3]wherein L⁺ represents any onium cation, and X⁻ represents a counteranion selected from the group consisting of PF₆ ⁻, SbF₆ ⁻, AsF₆ ⁻, SbCl₆⁻, BiCl₅ ⁻, SnCl₆ ⁻, ClO₄ ⁻, dithiocarbamate anion, and SCN⁻.

Preferred examples of the onium salt that forms the photo-acid generatorinclude onium salts including any anion selected from PF₆ ⁻, SbF₆ ⁻,AsF₆ ⁻, SbCl₆ ⁻, BiCl₅ ⁻, SnCl₆ ⁻, ClO₄ ⁻, dithiocarbamate anion, andSCN⁻.

More specifically, preferred examples of the photo-acid generatorinclude CYRACURE UVI-6992 and CYRACURE UVI-6974 (all manufactured by TheDow Chemical Company), ADEKA OPTOMER SP150, ADEKA OPTOMER SP152, ADEKAOPTOMER SP170, and ADEKA OPTOMER SP172 (all manufactured by ADEKACORPORATION), IRGACURE 250 (manufactured by Ciba Specialty ChemicalsInc.), CI-5102 and CI-2855 (all manufactured by Nippon Soda Co., Ltd.),SAN-AID SI-60L, SAN-AID SI-80L, SAN-AID SI-100L, SAN-AID SI-110L, andSAN-AID SI-180L (all manufactured by SANSHIN CHEMICAL INDUSTRY CO.,LTD.), CPI-100P and CPI-100A (all manufactured by SAN-APRO LTD.), andWPI-069, WPI-113, WPI-116, WPI-041, WPI-044, WPI-054, WPI-055, WPAG-281,WPAG-567, and WPAG-596 (all manufactured by Wako Pure ChemicalIndustries, Ltd.).

The content of the photo-acid generator should be 10 parts by weight orless based on 100 parts by weight of the total amount of the curablecomponents, and is preferably from 0.01 to 10 parts by weight, morepreferably from 0.05 to 5 parts by weight, even more preferably from 0.1to 3 parts by weight, based on 100 parts by weight of the total amountof the curable components.

A process of forming the transparent layer from the curable,layer-forming material may include applying the curable, layer-formingmaterial to the surface of the polarizer and then curing the appliedmaterial.

The polarizer may be subjected to a surface modification treatmentbefore the curable, layer-forming material is applied thereto.Specifically, such a treatment may be, for example, a corona treatment,a plasma treatment, or a saponification treatment.

The method for applying the curable, layer-forming material isappropriately selected depending on the viscosity of the curable,layer-forming material or the desired thickness. Examples of applicationmeans include a reverse coater, a gravure coater (direct, reverse, oroffset), a bar reverse coater, a roll coater, a die coater, a barcoater, and a rod coater. Any other suitable application method such asdipping may also be used.

<Curing of Layer-Forming Material>

The curable, layer-forming material may be used as an active energyray-curable, layer-forming material or a thermosetting, layer-formingmaterial. The active energy ray-curable, layer-forming material may beof an electron beam-curable type, an ultraviolet-curable type, or avisible light-curable type. In view of productivity, an active energyray-curable, layer-forming material is more preferred as the curable,layer-forming material than a thermosetting, layer-curable material.Also in view of productivity, a visible light-curable, layer-formingmaterial is more preferred as the active energy ray-curable,layer-forming material.

<<Active Energy Ray-Curable Type>>

When the active energy ray-curable, layer-forming material is used, theactive energy ray-curable, layer-forming material may be applied to thepolarizer and then irradiated with active energy rays (such as electronbeams, ultraviolet rays, or visible rays) so that the active energyray-curable, layer-forming material can be cured to form the transparentlayer. Active energy rays (such as electron beams, ultraviolet rays, orvisible rays) may be applied in any suitable direction. Preferably,active energy rays are applied from the transparent layer side.

<<Electron Beam-Curable Type>>

When the active energy ray-curable, layer-forming material is of anelectron beam-curable type, electron beams may be applied under anyappropriate conditions where the active energy ray-curable,layer-forming material can be cured. For example, electron beams arepreferably applied at an acceleration voltage of 5 kV to 300 kV, morepreferably 10 kV to 250 kV. If the acceleration voltage is lower than 5kV, electron beams may fail to reach the deepest portion of thetransparent layer, so that insufficient curing may occur. If theacceleration voltage is higher than 300 kV, electron beams can have toohigh intensity penetrating through the material and thus may damage thetransparent protective film or the polarizer. The exposure dose ispreferably from 5 to 100 kGy, more preferably from 10 to 75 kGy. At anexposure dose of less than 5 kGy, the adhesive may be insufficientlycured. An exposure dose of more than 100 kGy may damage the transparentprotective film or the polarizer and cause yellow discoloration or areduction in mechanical strength, which may make it impossible to obtainthe desired optical properties.

Electron beam irradiation is generally performed in an inert gas. Ifnecessary, however, electron beam irradiation may be performed in theair or under conditions where a small amount of oxygen is introduced.

<<Ultraviolet-Curable Type and Visible Light-Curable Type>>

In a method for producing the polarizing film according to theinvention, the active energy rays used preferably include visible raysin the wavelength range of 380 nm to 450 nm, specifically, visible rayswhose dose is the highest in the wavelength range of 380 nm to 450 nm.In the invention, the active energy ray source is preferably agallium-containing metal halide lamp or an LED light source capable ofemitting light in the wavelength range of 380 to 440 nm. Alternatively,a low-pressure mercury lamp, a middle-pressure mercury lamp, ahigh-pressure mercury lamp, an ultrahigh-pressure mercury lamp, anincandescent lamp, a xenon lamp, a halogen lamp, a carbon arc lamp, ametal halide lamp, a fluorescent lamp, a tungsten lamp, a gallium lamp,an excimer laser, or a source of light including ultraviolet and visiblerays, such as sunlight, may be used, and light sources may be used incombination with a band pass filter to block ultraviolet rays withwavelengths shorter than 380 nm.

<<Thermosetting Type>>

On the other hand, when the thermosetting, layer-forming material isused, it may be heated after the polarizer and the transparentprotective film are bonded together so that the thermal polymerizationinitiator can initiate the polymerization to form a cured product layer.The heating temperature may be from about 60 to about 200° C.,preferably from 80 to 150° C., though it is selected depending on thethermal polymerization initiator.

For example, a cyanoacrylate-based, layer-forming material, anepoxy-based, layer-forming material, or an isocyanate-based,layer-forming material may also be used as a material for forming thetransparent layer.

Examples of the cyanoacrylate-based, layer-forming material includealkyl-α-cyanoacrylates such as methyl-α-cyanoacrylate,ethyl-α-cyanoacrylate, butyl-α-cyanoacrylate, and octyl-α-cyanoacrylate,and cyclohexyl-α-cyanoacrylate and methoxy-α-cyanoacrylate. Thecyanoacrylate-based, layer-forming material may be, for example, oneused as a cyanoacrylate-based adhesive.

An epoxy resin may be used alone for the epoxy-based, layer-formingmaterial, or an epoxy curing agent may be added to an epoxy resin forthe epoxy-based, layer-forming material. When an epoxy resin is usedalone, a photopolymerization initiator should be added to theepoxy-based, layer-forming material so that the material can be cured byapplication of active energy rays. When an epoxy curing agent is addedto the epoxy-based, layer-forming material, the epoxy curing agent maybe, for example, one used for epoxy-based adhesives. The epoxy-based,layer-forming material should be used in the form of a two-componentsystem, in which a curing agent is added to an epoxy resin, though itmay also be used in the form of a one-component system, which containsan epoxy resin and a curing agent therefor. The epoxy-based,layer-forming material is generally used in the form of a solution. Thesolution may be a solvent-based solution, an emulsion, a colloidaldispersion, or a water-based solution such as an aqueous solution.

Examples of the epoxy resin may include a variety of compounds havingtwo or more epoxy groups per molecule, such as bisphenol type epoxyresins, aliphatic-based epoxy resins, aromatic-based epoxy resins,halogenated bisphenol type epoxy resins, and biphenyl-based epoxyresins. The epoxy resin may be appropriately selected depending on theepoxy equivalent or the number of functional groups. In view ofdurability, epoxy resins with an epoxy equivalent of 500 or less arepreferably used.

The curing agent for the epoxy resin may be any of various types, suchas a phenolic resin-based curing agent, an acid anhydride-based curingagent, a carboxylic acid-based curing agent, and a polyamine-basedcuring agent. Examples of the phenolic resin-based curing agent that maybe used include phenol novolac resins, bisphenol novolac resins,xylylene phenol resins, and cresol novolac resins. Examples of the acidanhydride-based curing agent include maleic anhydride,tetrahydrophthalic anhydride, hexahydrophthalic anhydride, and succinicanhydride. Examples of the carboxylic acid-based curing agent includecarboxylic acids such as pyromellitic acid and trimellitic acid; andblocked carboxylic acids formed by addition of vinyl ether to carboxylicacids. The two component-type, epoxy-based, layer-forming material maybe, for example, a combination of two components including an epoxyresin and a polythiol, or a combination of two components including anepoxy resin and a polyamide.

The content of the curing agent is preferably from 30 to 70 parts byweight, more preferably from 40 to 60 parts by weight, based on 100parts by weight of the epoxy resin, though it may vary with the epoxyresin equivalent.

The epoxy-based, layer-forming material may also contain any of variouscuring accelerators in addition to the epoxy resin and the curing agenttherefor. Examples of curing accelerators include variousimidazole-based compounds and derivatives thereof, and dicyandiamide.

The isocyanate-based, layer-forming material may be a crosslinking agentused in the formation of pressure-sensitive adhesive layers. A compoundhaving at least two isocyanate groups may be used as such anisocyanate-based crosslinking agent. For example, the polyisocyanatecompound may be used as the isocyanate-based, layer-forming material.Specific examples thereof include 2,4-tolylene diisocyanate,2,6-tolylene diisocyanate, xylylene diisocyanate,1,3-bisisocyanatomethylcyclohexane, hexamethylene diisocyanate,tetramethylxylylene diisocyanate, m-isopropenyl-α,α-dimethylbenzylisocyanate, methylene bis(4-phenyl isocyanate), p-phenylenediisocyanate, or dimers thereof, trimers such as tris(6-isocyanatohexyl)isocyanurate, and reaction products thereof with a polyhydric alcohol ora polyamine, such as biuret or trimethylolpropane. The isocyanate-basedcrosslinking agent is also preferably a compound having three or moreisocyanate groups, such as tris(6-isocyanatehexyl) isocyanurate.Examples of the isocyanate-based, layer-forming material include thoseused as isocyanate-based adhesives.

In particular, an isocyanate-based, layer-forming material having arigid structure in which a cyclic structure (such as a benzene ring, acyanurate ring, or an isocyanurate ring) makes up a large part of themolecular structure is preferably used. For example,trimethylolpropane-tri-tolyleneisocyanate ortris(hexamethyleneisocyanate) isocyanurate is preferably used for theisocyanate-based, layer-forming material.

The isocyanate-based crosslinking agent to be used may have a protectinggroup attached to the terminal isocyanate group. The protecting groupmay be, for example, an oxime or a lactam. The protecting group attachedto the isocyanate group can be dissociated from the isocyanate group byheating, so that the isocyanate group becomes available for reaction.

A reaction catalyst may be further used to enhance the reactivity of theisocyanate group. Such a reaction catalyst is preferably, but notlimited to, a tin-based catalyst or an amine-based catalyst. One or twoor more reaction catalysts may be used. The reaction catalyst isgenerally used in an amount of 5 parts by weight or less based on 100parts by weight of the isocyanate crosslinking agent. If the amount ofthe reaction catalyst is large, the crosslinking reaction rate may behigh so that the layer-forming material may foam. If the foamed,layer-forming material is used, sufficient adhesion cannot be obtained.In general, the reaction catalyst is preferably used in an amount of0.01 to 5 parts by weight, more preferably 0.05 to 4 parts by weight.

The tin-based catalyst may be any of an inorganic tin-based catalyst andan organo-tin-based catalyst. Preferably, the tin-based catalyst is anorgano-tin-based catalyst. The inorganic tin-based catalyst may be, forexample, stannous chloride or stannic chloride. The organo-tin-basedcatalyst preferably has at least one organic group such as an aliphaticor alicyclic group having a methyl, ethyl, ether, ester, or any othergroup in the skeleton. Specific examples thereof includetetra-n-butyltin, tri-n-butyltin acetate, n-butyltin trichloride,trimethyltin hydroxide, dimethyltin dichloride, and dibutyltindilaurate.

The amine-based catalyst may also be of any type. For example, the aminecatalyst preferably has an organic group such as quinocridine, amidine,diazabicycloundecene, or any other alicyclic group. In addition, theamine-based catalyst may also be triethylamine. Besides the above,examples of the reaction catalyst also include cobalt naphthenate andbenzyltrimethylammonium hydroxide.

The isocyanate-based, layer-forming material is generally used in theform of a solution. The solution may be a solvent-based solution, awater-based solution such as an emulsion, a colloidal dispersion and anaqueous solution. Any organic solvent capable of uniformly dissolvingthe components of the layer-forming material may be used. Examples ofsuch an organic solvent include toluene, methyl ethyl ketone, and ethylacetate. When a water-based solution is formed, for example, an alcoholsuch as n-butyl alcohol or isopropyl alcohol or a ketone such as acetonemay also be added to the water-based solution. When a water-basedsolution is formed, a dispersing agent may be used, or a functionalgroup less reactive with the isocyanate group, such as a carboxylatesalt, a sulfonate salt, or a quaternary ammonium salt, or awater-dispersible component such as polyethylene glycol may beintroduced into the isocyanate crosslinking agent.

The conditions for forming the transparent layer from thecyanoacrylate-based, epoxy-based, or isocyanate-based, layer-formingmaterial may be appropriately selected depending on the type of thelayer-forming material. In general, the transparent layer can be formedby drying the layer-forming material at about 30 to about 100° C.,preferably at 50 to 80° C., for about 0.5 to about 15 minutes. When thecyanoacrylate-based, layer-forming material is used, the transparentlayer can be formed in a time shorter than the above time because thematerial can be cured faster.

The transparent layer may also be formed from a layer-forming materialcontaining no curable component. For example, the transparent layer mayalso be formed from a layer-forming material including the polyvinylalcohol-based resin as a main component. The polyvinyl alcohol-basedresin used to form the transparent layer may be the same as or differentfrom the polyvinyl alcohol-based resin in the polarizer as long as itfalls under the category of “polyvinyl alcohol-based resin.”

The polyvinyl alcohol-based resin may be, for example, polyvinylalcohol. Polyvinyl alcohol can be obtained by saponifying polyvinylacetate. The polyvinyl alcohol-based resin may also be a productproduced by saponifying a copolymer of vinyl acetate and any othermonomer or monomers copolymerizable therewith. In this case, when thecopolymerizable monomer is ethylene, an ethylene-vinyl alcohol copolymercan be obtained. Examples of the copolymerizable monomer includeunsaturated carboxylic acids such as maleic acid (anhydride), fumaricacid, crotonic acid, itaconic acid, and (meth)acrylic acid, and estersthereof; α-olefins such as ethylene and propylene; (sodium)(meth)allylsulfonate, sodium sulfonate (monoalkyl maleate), sodiumdisulfonate alkyl maleate, N-methylolacrylamide, acrylamide alkylsulfonate alkali salts, N-vinylpyrrolidone, and N-vinylpyrrolidonederivatives. These polyvinyl alcohol-based resins may be used alone orin combination of two or more. The heat of crystal fusion of thetransparent layer should be controlled to 30 mj/mg or more so that thetransparent layer can have a satisfactory level of moist heat resistanceor water resistance. From this point of view, the polyvinylalcohol-based resin is preferably polyvinyl alcohol obtained bysaponifying polyvinyl acetate.

The polyvinyl alcohol-based resin to be used may have a saponificationdegree of, for example, 95% or more. In order to control the heat ofcrystal fusion of the transparent layer to 30 mj/mg or more so that itcan have a satisfactory level of moist heat resistance or waterresistance, the polyvinyl alcohol-based resin preferably has asaponification degree of 99.0% or more, more preferably 99.7% or more.The saponification degree indicates the proportion of the units actuallysaponified to vinyl alcohol units in the units capable of beingconverted to vinyl alcohol units by saponification, after which vinylester units can remain as residues. The saponification degree can bedetermined according to JIS K 6726-1994.

The polyvinyl alcohol-based resin to be used may have an average degreeof polymerization of, for example, 500 or more. In order to control theheat of crystal fusion of the transparent layer to 30 mj/mg or more sothat it can have a satisfactory level of moist heat resistance or waterresistance, the polyvinyl alcohol-based resin preferably has an averagedegree of polymerization of 1,000 or more, more preferably 1,500 ormore, even more preferably 2,000 or more. The average degree ofpolymerization of the polyvinyl alcohol-based resin can be measuredaccording to JIS K 6726.

The polyvinyl alcohol-based resin to be used may also be a modifiedpolyvinyl alcohol-based resin having a hydrophilic functional group onthe side chain of the polyvinyl alcohol or copolymerized polyvinylalcohol. The hydrophilic functional group may be, for example, anacetoacetyl group or a carbonyl group. Other examples of the polyvinylalcohol resin that may be used include modified polyvinyl alcoholsobtained by, for example, acetalization, urethanation, etherification,or phosphorylation of polyvinyl alcohol resin or grafting on polyvinylalcohol resin.

The layer-forming material containing the polyvinyl alcohol-based resinas a main component may contain a curable component (crosslinkingagent). The content of the polyvinyl alcohol-based resin in thetransparent layer or the layer-forming material (solid basis) ispreferably 80% by weight or more, more preferably 90% by weight or more,even more preferably 95% by weight or more. In order to make it easy tocontrol the heat of crystal fusion of the transparent layer to 30 mj/mgor more, the layer-forming material is preferably free of any curablecomponent (crosslinking agent).

A compound having at least two functional groups reactive with thepolyvinyl alcohol-based resin may be used as the crosslinking agent.Examples of such a compound include alkylenediamines having an alkylenegroup and two amino groups, such as ethylenediamine, triethylenediamine,and hexamethylenediamine; isocyanates such as tolylene diisocyanate,hydrogenated tolylene diisocyanate, trimethylolpropane tolylenediisocyanate adducts, triphenylmethane triisocyanate, methylenebis(4-phenylmethanetriisocyanate, isophorone diisocyanate, and ketoximeblocked compounds thereof or phenol blocked compounds thereof; epoxiessuch as ethylene glycol diglycidyl ether, polyethylene glycol diglycidylether, glycerin di- or triglycidyl ether, 1,6-hexanediol diglycidylether, trimethylolpropane triglycidyl ether, diglycidyl aniline, anddiglycidyl amine; monoaldehydes such as formaldehyde, acetaldehyde,propionaldehyde, and butylaldehyde; dialdehydes such as glyoxal,malondialdehyde, succindialdehyde, glutardialdehyde, maleic dialdehyde,and phthaldialdehyde; amino-formaldehyde resins such as condensates offormaldehyde with methylolurea, methylolmelamine, alkylatedmethylolurea, alkylated methylolmelamine, acetoguanamine, orbenzoguanamine; dicarboxylic acid dihydrazides such as adipic aciddihydrazide, oxalic acid dihydrazide, malonic acid dihydrazide, succinicacid dihydrazide, glutaric acid dihydrazide, isophthalic aciddihydrazide, sebacic acid dihydrazide, maleic acid dihydrazide, fumaricacid dihydrazide, and itaconic acid dihydrazide; and water-solubledihydrazines such as ethylene-1,2-dihydrazine,propylene-1,3-dihydrazine, and butylene-1,4-dihydrazine. Among them,amino-formaldehyde resins and water-soluble dihydrazines are preferred.The amino-formaldehyde resins are preferably methylol group-containingcompounds. Methylolmelamine is particularly preferred among the methylolgroup-containing compounds.

The curable component (crosslinking agent) may be used to improve waterresistance, in which the content of the curable component (crosslinkingagent) is preferably 20 parts by weight or less, 10 parts by weight orless, or 5 parts by weight or less, based on 100 parts by weight of thepolyvinyl alcohol-based resin.

The layer-forming material may be prepared as a solution by dissolvingthe polyvinyl alcohol-based resin in a solvent. Examples of the solventinclude water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide,N-methylpyrrolidone, various glycols, alcohols including polyhydricalcohols, and amines such as ethylenediamine and diethylenetriamine.These solvents may be used alone or in combination of two or more. Amongthem, water is preferably used as the solvent to form the layer-formingmaterial as an aqueous solution. The concentration of the polyvinylalcohol-based resin in the layer-forming material (e.g., an aqueoussolution) may be, but not limited to, 0.1 to 15% by weight, preferably0.5 to 10% by weight, in view of coatability, shelf stability, and otherproperties.

The layer-forming material (e.g., an aqueous solution) may contain anadditive such as a plasticizer or a surfactant. The plasticizer may be,for example, a polyhydric alcohol such as ethylene glycol or glycerin.The surfactant may be, for example, a nonionic surfactant. Thelayer-forming material may also contain a coupling agent such as asilane coupling agent or a titanium coupling agent, any of varioustackifiers, an ultraviolet absorber, an antioxidant, and a stabilizersuch as a heat-resistant stabilizer or a hydrolysis-resistantstabilizer.

The transparent layer may be formed by applying the layer-formingmaterial to the other surface of the polarizer (the surface opposite toits surface on which the transparent protective film is placed) anddrying the material. The application process is not limited, and anyappropriate method may be used in the application process. For example,roll coating, spin coating, wire bar coating, dip coating, die coating,curtain coating, spray coating, knife coating, (such as comma coating),or various other methods may be used.

<Pressure-Sensitive Adhesive Layer>

The pressure-sensitive adhesive layer may be formed using anyappropriate type of pressure-sensitive adhesive. Examples of thepressure-sensitive adhesive include a rubber-based pressure-sensitiveadhesive, an acryl-based pressure-sensitive adhesive, a silicone-basedpressure-sensitive adhesive, a urethane-based pressure-sensitiveadhesive, a vinyl alkyl ether-based pressure-sensitive adhesive, apolyvinyl alcohol-based pressure-sensitive adhesive, apolyvinylpyrrolidone-based pressure-sensitive adhesive, apolyacrylamide-based pressure-sensitive adhesive, and a cellulose-basedpressure-sensitive adhesive.

Among these pressure-sensitive adhesives, those having a high level ofoptical transparency and weather resistance or heat resistance andexhibiting an appropriate level of wettability and adhesive propertiessuch as cohesiveness and adhesiveness are preferably used. Anacryl-based pressure-sensitive adhesive is preferably used because ithas such properties.

The pressure-sensitive adhesive layer can be formed by a methodincluding applying the pressure-sensitive adhesive to a release-treatedseparator or other means, removing the polymerization solvent and othercomponents from the adhesive by drying to form a pressure-sensitiveadhesive layer, and then transferring the pressure-sensitive adhesivelayer onto the polarizer in the embodiment of FIG. 2A (or onto thetransparent protective film in the embodiment of FIG. 2B).Alternatively, the pressure-sensitive adhesive layer can be formed by amethod including applying the pressure-sensitive adhesive to thepolarizer in the embodiment of FIG. 2A (or to the transparent protectivefilm in the embodiment of FIG. 2B) and removing the polymerizationsolvent and other components from the adhesive by drying to form apressure-sensitive adhesive layer on the polarizer. In the process ofapplying the pressure-sensitive adhesive, if necessary, one or moresolvents other than the polymerization solvent may be newly added to theadhesive.

A silicone release liner is preferably used as the release-treatedseparator. In the invention, the pressure-sensitive adhesive may beapplied to such a liner and then dried to form a pressure-sensitiveadhesive layer. In this process, any appropriate method may be used fordrying the pressure-sensitive adhesive, depending on purpose.Preferably, a method of heating and drying the coating film is used. Theheating and drying temperature is preferably from 40° C. to 200° C.,more preferably from 50° C. to 180° C., even more preferably from 70° C.to 170° C. When the heating temperature is set in the range, apressure-sensitive adhesive with a high level of adhesive properties canbe obtained.

Any appropriate drying time may be used as needed. The drying time ispreferably from 5 seconds to 20 minutes, more preferably from 5 secondsto 10 minutes, even more preferably from 10 seconds to 5 minutes.

Various methods may be used to form the pressure-sensitive adhesivelayer. Examples of such methods include roll coating, kiss roll coating,gravure coating, reverse coating, roll brush coating, spray coating, diproll coating, bar coating, knife coating, air knife coating, curtaincoating, lip coating, and extrusion coating with a die coater or othermeans.

The thickness of the pressure-sensitive adhesive layer is typically, butnot limited to, about 1 to about 100 μm, preferably 2 to 50 μm, morepreferably 2 to 40 μm, even more preferably 5 to 35 μm.

When the pressure-sensitive adhesive layer is exposed, thepressure-sensitive adhesive layer may be protected by a release-treatedsheet (separator) until it is actually used.

Examples of the material used to form such a separator include a plasticfilm such as a polyethylene, polypropylene, polyethylene terephthalate,or polyester film, a paper, a cloth, a porous material such as nonwovenfabric, and appropriate thin materials such as a net, a foamed sheet, ametal foil, and any laminate thereof. A plastic film is preferably usedbecause of its good surface smoothness.

Such a plastic film may be of any type capable of protecting thepressure-sensitive adhesive layer. Such a plastic film may be, forexample, a polyethylene film, a polypropylene film, a polybutene film, apolybutadiene film, a polymethylpentene film, a polyvinyl chloride film,a vinyl chloride copolymer film, a polyethylene terephthalate film, apolybutylene terephthalate film, a polyurethane film, or anethylene-vinyl acetate copolymer film.

The separator generally has a thickness of about 5 to about 200 μm,preferably about 5 to about 100 μm. If necessary, the separator may besubjected to a release treatment and an anti-pollution treatment with asilicone-based, fluoride-based, long-chain alkyl-based, or fatty acidamide-based release agent, a silica powder, or other materials, orsubjected to an antistatic treatment of coating type, kneading andmixing type, vapor-deposition type, or other types. In particular, whenthe surface of the separator is appropriately subjected to a releasetreatment such as a silicone treatment, a long-chain alkyl treatment, ora fluorine treatment, the releasability from the pressure-sensitiveadhesive layer can be further improved.

<Surface Protective Film>

A surface protective film may be provided on the one-side-protectedpolarizing film or the pressure-sensitive-adhesive-layer-attachedpolarizing film. The surface protective film generally has a base filmand a pressure-sensitive adhesive layer. The surface protective filmprotects the polarizer with the pressure-sensitive adhesive layerinterposed between them.

In view of the ability to be tested or managed, an isotropic ornearly-isotropic film material should be selected as the base film forthe surface protective film. Examples of such a film material includepolyester-based resins such as polyethylene terephthalate films,cellulose-based resins, acetate-based resins, polyethersulfone-basedresins, polycarbonate-based resins, polyamide-based resins,polyimide-based resins, polyolefin-based resins, acryl-based resins, andother transparent polymers. In particular, polyester-based resins arepreferred. The base film may be made of a single film material or alaminate of two or more film materials. The base film may also be aproduct obtained by stretching the film. The base film generally has athickness of 500 μm or less, preferably 10 to 200 μm.

The pressure-sensitive adhesive used to form the pressure-sensitiveadhesive layer for the surface protective film may be appropriatelyselected from pressure-sensitive adhesives including, as a base polymer,a (meth)acryl-based polymer, a silicone-based polymer, polyester,polyurethane, polyamide, polyether, fluoride-based polymer, rubber-basedpolymer, or any other polymer. An acryl-based pressure-sensitiveadhesive containing an acryl-based polymer as a base polymer ispreferred in view of transparency, weather resistance, heat resistance,and other properties. The thickness (dry thickness) of thepressure-sensitive adhesive layer is selected depending on the desiredadhesive strength. The thickness of the pressure-sensitive adhesive isgenerally from about 1 to about 100 μm, preferably from 5 to 50 μm.

A silicone, long-chain alkyl, or fluorine treatment with a low-adhesionmaterial may also be performed to form a release treatment layer on thesurface of the base film of the surface protective film, opposite to itssurface on which the pressure-sensitive adhesive layer is provided.

<Other Optical Layers>

For practical use, the one-side-protected polarizing film of theinvention or the pressure-sensitive-adhesive-layer-attached polarizingfilm of the invention may be laminated with any other optical layer orlayers to form an optical film. As a non-limiting example, such anoptical layer or layers may be one or more optical layers that have everbeen used to form liquid crystal display devices or other devices, suchas a reflector, a transflector, a retardation plate (including awavelength plate such as a half or quarter wavelength plate), or aviewing angle compensation film. Particularly preferred is a reflectiveor transflective polarizing film including a laminate of theone-side-protected polarizing film of the invention and a reflector or atransflector, an elliptically or circularly polarizing film including alaminate of the polarizing film of the invention and a retardationplate, a wide viewing angle polarizing film including a laminate of thepolarizing film of the invention and a viewing angle compensation film,or a polarizing film including a laminate of the polarizing film of theinvention and a brightness enhancement film.

The optical film including a laminate of the above optical layer and theone-side-protected polarizing film or thepressure-sensitive-adhesive-layer-attached polarizing film may be formedby a method of stacking them one by one, for example, in the process ofmanufacturing a liquid crystal display device. However, the optical filmshould be formed by stacking them in advance, which is superior inquality stability or assembling workability and thus advantageous infacilitating the process of manufacturing liquid crystal display devicesor other devices. In the lamination, any appropriate bonding means suchas a pressure-sensitive adhesive layer may be used. When thepressure-sensitive-adhesive-layer-attached polarizing film and any otheroptical film are bonded together, their optical axes may be each alignedat an appropriate angle, depending on the desired retardation propertiesor other desired properties.

The one-side-protected polarizing film, thepressure-sensitive-adhesive-layer-attached polarizing film, or theoptical film according to the invention is preferably used to formvarious image display devices such as liquid crystal display devices andorganic EL display devices. Liquid crystal display devices may be formedaccording to conventional techniques. Specifically, a liquid crystaldisplay device may be typically formed according to any conventionaltechniques by appropriately assembling a liquid crystal cell,pressure-sensitive-adhesive-layer-attached polarizing films or opticalfilms, and optional components such as a lighting system, incorporatinga driving circuit, and performing other processes, except that theone-side-protected polarizing film, thepressure-sensitive-adhesive-layer-attached polarizing film, or theoptical film according to the invention is used. The liquid crystal cellto be used may also be of any type, such as IPS type or VA type. Theinvention is particularly suitable for IPS type.

Any desired liquid crystal display device may be formed, such as aliquid crystal display device including a liquid crystal cell and theone-side-protected polarizing film or films, thepressure-sensitive-adhesive-layer-attached polarizing film or films, orthe optical film or films placed on one or both sides of the liquidcrystal cell, or a liquid crystal display device further including abacklight or a reflector in the lighting system. In such a case, thepressure-sensitive-adhesive-layer-attached polarizing film or films orthe optical film or films according to the invention may be placed onone or both sides of the liquid crystal cell. When theone-side-protected polarizing films, thepressure-sensitive-adhesive-layer-attached polarizing films, or theoptical films are provided on both sides, they may be the same ordifferent. The process of forming the liquid crystal display device mayalso include placing, at an appropriate position or positions, one ormore layers of an appropriate component such as a diffusion plate, anantiglare layer, an anti-reflection film, a protective plate, a prismarray, a lens array sheet, a light diffusion plate, or a backlight.

<Method for Continuously Producing Image Display Device>

The image display device described above is preferably produced by acontinuous production method (roll-to-panel process) including the stepsof: unwinding the pressure-sensitive-adhesive-layer-attached polarizingfilm of the invention from a roll thereof; feeding thepressure-sensitive-adhesive-layer-attached polarizing film with theseparator; and continuously bonding thepressure-sensitive-adhesive-layer-attached polarizing film to thesurface of an image display panel with the pressure-sensitive adhesivelayer interposed therebetween. Thepressure-sensitive-adhesive-layer-attached polarizing film of theinvention is a very thin film. Therefore, if thepressure-sensitive-adhesive-layer-attached polarizing film of theinvention is subjected to a process that includes cutting the film intosheet pieces (cut pieces) and then bonding the pieces one by one toimage display panels (also referred to as a “sheet-to-panel process”),the sheets will be difficult to feed or handle during the bonding ofthem to the display panels, so that the risk for thepressure-sensitive-adhesive-layer-attached polarizing films (sheets) toundergo high mechanical shock (such as suction-induced bending) willincrease during these processes. In order to reduce the risk, othermeasures should be taken, such as using a relatively thick surfaceprotective film including a base film with a thickness of 50 μm or more.In contrast, the roll-to-panel process allows thepressure-sensitive-adhesive-layer-attached polarizing film to be stablyfed from the roll to the image display panel with the aid of theseparator, without cutting the film into sheet pieces (cut pieces), andalso allows the film to be directly bonded to the image display panel,which makes it possible to significantly reduce the risk without using arelatively thick surface protective film. This allows high-speedcontinuous production of image display devices so as to effectivelysuppress not only defects which would otherwise be caused by theoccurrence of nano-slits before the formation of the transparent layerbut also defects which would otherwise be caused by the occurrence ofnano-slits after the formation of the transparent layer.

FIG. 8 is a schematic diagram illustrating an example of a system forcontinuously producing liquid crystal devices using the roll-to-panelprocess.

As illustrated in FIG. 8, a system 100 for continuously producing liquidcrystal display devices includes a continuous feed unit X configured tofeed liquid crystal display panels P, a first polarizing film supplyunit 101 a, a first bonding unit 201 a, a second polarizing film supplyunit 101 b, and a second bonding unit 201 b.

In this case, a roll 20 a of a firstpressure-sensitive-adhesive-layer-attached polarizing film (a firstroll) and a roll 20 b of a secondpressure-sensitive-adhesive-layer-attached polarizing film (a secondroll) are used, in which the films each have an absorption axis in thelongitudinal direction and each have the structure shown in FIG. 2A.

(Feed Unit)

The feed unit X is configured to feed liquid crystal display panels P.The feed unit X includes a plurality of feed rollers, suction plates,and other components. The feed unit X includes an orientation changingunit 300 that is provided between the first and second bonding units 201a and 201 b and configured to interchange the positional relationshipbetween the long and short sides of the liquid crystal panel P withrespect to the direction of the feed of the liquid crystal display panelP (e.g., by horizontally turning the liquid crystal display panel P by90°). This allows the first and secondpressure-sensitive-adhesive-layer-attached polarizing films 21 a and 21b to be bonded in a cross-Nicols relationship to the liquid crystaldisplay panel P.

(First Polarizing Film Supply Unit)

The first polarizing film supply unit 101 a is configured to unwind thefirst pressure-sensitive-adhesive-layer-attached polarizing film 21 a(with a surface protective film) from the first roll 20 a, feed the film21 a with the separator 5 a, and continuously supply the film 21 a tothe first bonding unit 201 a. The first polarizing film supply unit 101a includes a first unwinding unit 151 a, a first cutting unit 152 a, afirst peeling unit 153 a, a first winding unit 154 a, a plurality offeed roller units, an accumulator unit including dancer rolls, and othercomponents.

The first unwinding unit 151 a has an unwinding shaft on which the firstroll 20 a is placed, and is configured to unwind, from the first roll 20a, the long, pressure-sensitive-adhesive-layer-attached, polarizing film21 a provided with the separator 5 a.

The first cutting unit 152 a includes cutting means such as a cutter ora laser and suction means. The first cutting unit 152 a is configured toform a piece with a predetermined length by transversely cutting thefirst long pressure-sensitive-adhesive-layer-attached polarizing film 21a and leaving the separator 5 a uncut. Alternatively, the first roll 20a may be a roll of a laminate of the separator 5 a and the longpressure-sensitive-adhesive-layer-attached polarizing film with aplurality of score lines formed in the widthwise direction atpredetermined intervals (a scored optical film roll). In this case, thefirst cutting unit 152 a is unnecessary (this also applies to the secondcutting unit 152 b described below).

The first peeling unit 153 a is configured to peel off the firstpressure-sensitive-adhesive-layer-attached polarizing film 21 a from theseparator 5 a by inwardly folding back the separator 5 a. The firstpeeling unit 153 a may include a wedge-shaped member, rollers, and othercomponents.

The first winding unit 154 a is configured to wind the separator 5 afrom which the first pressure-sensitive-adhesive-layer-attachedpolarizing film 21 a has been peeled off. The first winding unit 154 ahas a winding shaft on which a roll for winding the separator 5 a isplaced.

(First Bonding Unit)

The first bonding unit 201 a is configured to continuously bond thefirst pressure-sensitive-adhesive-layer-attached polarizing film 21 a,which has been peeled off by the first peeling unit 153 a, to the liquidcrystal display panel P, which is being fed by the feed unit X, with thepressure-sensitive adhesive layer of the firstpressure-sensitive-adhesive-layer-attached polarizing film 21 ainterposed therebetween (first bonding step). The first bonding unit 81includes a pair of bonding rollers, at least one of which includes adrive roller.

(Second Polarizing Film Supply Unit)

The second polarizing film supply unit 101 b is configured to unwind thesecond pressure-sensitive-adhesive-layer-attached polarizing film 21 b(with a surface protective film) from the second roll 20 b, feed thefilm 21 b with the separator 5 b, and continuously supply the film 21 bto the second bonding unit 201 b. The second polarizing film supply unit101 b includes a second unwinding unit 151 b, a second cutting unit 152b, a second peeling unit 153 b, a second winding unit 154 b, a pluralityof feed roller units, an accumulator unit including dancer rolls, andother components. The second unwinding unit 151 b, the second cuttingunit 152 b, the second peeling unit 153 b, and the second winding unit154 b have the same structures and functions as those of the firstunwinding unit 151 a, the first cutting unit 152 a, the first peelingunit 153 a, and the first winding unit 154 a, respectively.

(Second Bonding Unit)

The second bonding unit 201 b is configured to continuously bond thesecond pressure-sensitive-adhesive-layer-attached polarizing film 21 b,which has been peeled off by the second peeling unit 153 b, to theliquid crystal display panel P, which is being fed by the feed unit X,with the pressure-sensitive adhesive layer of the secondpressure-sensitive-adhesive-layer-attached polarizing film 21 binterposed therebetween (second bonding step). The second bonding unit201 b includes a pair of bonding rollers, at least one of which includesa drive roller (second bonding step).

EXAMPLES

Hereinafter, the invention will be more specifically described withreference to examples. It will be understood that the examples shownbelow are not intended to limit the invention. In each example, “parts”and “%” are all by weight. Unless otherwise specified below, theconditions of standing at room temperature include 23° C. and 65% RH inall cases.

<One-Side-Protected Polarizing Film A>

(Preparation of Polarizer A0)

A corona treatment was performed on one surface of an amorphousisophthalic acid-copolymerized polyethylene terephthalate(IPA-copolymerized PET) film substrate (100 μm in thickness) with awater absorption of 0.75% and a Tg of 75° C. An aqueous solutioncontaining polyvinyl alcohol (4,200 in polymerization degree, 99.2% bymole in saponification degree) and acetoacetyl-modified PVA (GohsefimerZ200 (trade name) manufactured by The Nippon Synthetic Chemical IndustryCo., Ltd., 1,200 in polymerization degree, 4.6% in acetoacetylmodification degree, 99.0% by mole or more in saponification degree) ina ratio of 9:1 was applied to the corona-treated surface at 25° C. andthen dried to form a 11-Cm-thick PVA-based resin layer, so that alaminate was formed.

In an oven at 120° C., the resulting laminate was subjected to free-enduniaxial stretching to 2.0 times in the longitudinal direction betweenrolls at different peripheral speeds (auxiliary in-air stretching).

Subsequently, the laminate was immersed in an insolubilization bath (anaqueous boric acid solution obtained by adding 4 parts by weight ofboric acid to 100 parts by weight of water) at a temperature of 30° C.for 30 seconds (insolubilization).

Subsequently, the laminate was immersed in a dyeing bath at atemperature of 30° C. while the iodine concentration and the immersiontime were so controlled as to allow the resulting polarizing plate tohave a predetermined transmittance. In this example, the laminate wasimmersed for 60 seconds in an aqueous iodine solution obtained by adding0.2 parts by weight of iodine and 1.0 part by weight of potassium iodideto 100 parts by weight of water (dyeing).

Subsequently, the laminate was immersed for 30 seconds in a crosslinkingbath (an aqueous boric acid solution obtained by adding 3 parts byweight of potassium iodide and 3 parts by weight of boric acid to 100parts by weight of water) at a temperature of 30° C. (crosslinking).

The laminate was then uniaxially stretched to a total stretch ratio of5.5 times in the longitudinal direction between rolls at differentperipheral speeds while it was immersed in an aqueous boric acidsolution (an aqueous solution obtained by adding 4 parts by weight ofboric acid and 5 parts by weight of potassium iodide to 100 parts byweight of water) at a temperature of 70° C. (in-water stretching).

The laminate was then immersed in a cleaning bath (an aqueous solutionobtained by adding 4 parts by weight of potassium iodide to 100 parts byweight of water) at a temperature of 30° C. (cleaning).

The resulting product was an optical film laminate including a5-μm-thick polarizer.

(Preparation of Polarizers A1 to A8)

Polarizers A1 to A8 were prepared similarly to the preparation ofpolarizer A0 described above, except that the preparation conditionswere changed as shown in Table 1. Table 1 also shows the thicknesses,optical properties (single-body transmittance and polarization degree),and boric acid concentrations of polarizers A1 to A8.

TABLE 1 Dyeing bath Polarizer PVA-based Potassium Boric resin AuxiliaryIodine iodide Single-body Polarization acid layer in-air content contentThickness trasmittance degree content thickness stretching (wt (wt (μm)T (%) P (%) (wt %) (μm) ratio parts) parts) Polarizer 5 42.8 99.99 16 11μm 2.0 times 0.2 parts 1.0 parts A0 Polarizer 5 42.8 99.99 14 11 μm 2.0times 0.2 parts 1.0 parts A1 Polarizer 5 42.8 99.99 18 11 μm 2.0 times0.2 parts 1.0 parts A2 Polarizer 5 42.8 99.99 20 11 μm 2.0 times 0.2parts 1.0 parts A3 Polarizer 3 42.8 99.99 16  7 μm 2.0 times 0.2 parts1.0 parts A4 Polarizer 7 42.8 99.99 16 15 μm 2.0 times 0.2 parts 1.0parts A5 Polarizer 5 44.1 99.99 16 11 μm 2.0 times 0.2 parts 1.0 partsA6 Polarizer 5 41.5 99.99 16 11 μm 2.0 times 0.2 parts 1.0 parts A7Polarizer 3.5 43.2 99.15 16  7 μm 4.0 times 0.2 parts 1.0 parts A8Cleaning In-water stretching bath bath Potassium Potassium iodide iodideDyeing bath content Total content Immersion Boric (wt Stretching stretch(wt time acid parts) ratio ratio parts) Polarizer 60 seconds 4.0 parts 5parts 2.75 times 5.5 times 4 parts A0 Polarizer 60 seconds 3.5 parts 5parts 2.75 times 5.5 times 4 parts A1 Polarizer 60 seconds 4.2 parts 5parts 2.75 times 5.5 times 4 parts A2 Polarizer 60 seconds 4.5 parts 5parts 2.75 times 5.5 times 4 parts A3 Polarizer 60 seconds 4.0 parts 5parts 2.75 times 5.5 times 4 parts A4 Polarizer 60 seconds 4.0 parts 5parts 2.75 times 5.5 times 4 parts A5 Polarizer 60 seconds 4.0 parts 5parts 2.75 times 5.5 times 4 parts A6 Polarizer 90 seconds 4.0 parts 5parts 2.75 times 5.5 times 4 parts A7 Polarizer 60 seconds   3 parts 3parts Not 4.0 times 4 parts A8 stretched

(Preparation of Transparent Protective Film)

The adhesion facilitation-treated surface of a lactone ringstructure-containing (meth)acrylic resin film with a thickness of 40 μmwas subjected to a corona treatment. The corona-treated film was used asa transparent protective film.

(Preparation of Adhesive to be Applied to Transparent Protective Film)

An ultraviolet-curable adhesive was prepared by mixing 40 parts byweight of N-hydroxyethylacrylamide (HEAA), 60 parts by weight ofacryloylmorpholine (ACMO), and 3 parts by weight of a photo-initiatorIRGACURE 819 (manufactured by BASF).

(Preparation of One-Side-Protected Polarizing Films A)

The transparent protective film was bonded to the surface of each ofpolarizers A0 to A8 of the optical film laminates with theultraviolet-curable adhesive being applied to the surface in such amanner as to form a 0.5-μm-thick adhesive layer after curing.Subsequently, the adhesive was cured by applying ultraviolet rays asactive energy rays. The ultraviolet rays were applied using thefollowing conditions: gallium-containing metal halide lamp; irradiator,Light Hammer 10 manufactured by Fusion UV Systems, Inc; valve, V valve;peak illuminance, 1,600 mW/cm^(z); total dose, 1,000/mJ/cm (wavelength380-440 nm). The illuminance of the ultraviolet rays was measured withSola-Check System manufactured by Solatell Ltd. Subsequently, theamorphous PET substrate was removed from each product, so thatone-side-protected polarizing films A0 to A8 each having the thinpolarizer were obtained. Table 2 shows the optical properties(single-body transmittance and polarization degree) of resultingone-side-protected polarizing films A0 to A8.

<One-Side-Protected Polarizing Film B>

(Preparation of Polarizer B (23-μm-Thick Polarizer))

A 75-μm-thick polyvinyl alcohol film with an average degree ofpolymerization of 2,400 and a degree of saponification of 99.9% by molewas immersed in warm water at 30° C. for 60 seconds so that it wasallowed to swell. Subsequently, the film was immersed in an aqueoussolution of 0.3% iodine/potassium iodide (0.5/8 in weight ratio) anddyed while stretched to 3.5 times. The film was then stretched to atotal stretch ratio of 6 times in an aqueous boric ester solution at 65°C. After the stretching, the film was dried in an oven at 40° C. for 3minutes to give a PVA-based polarizer (23 μm in thickness).

(Preparation of One-Side-Protected Polarizing Film B)

Similarly to the preparation of one-side-protected polarizing film A,the transparent protective film shown above was bonded to one surface ofthe PVA-based polarizer with the ultraviolet-curable adhesive shownabove. The optical properties of resulting one-side-protected film Bwere as follows: transmittance 42.8%, polarization degree 99.99%.

<One-Side-Protected Polarizing Film C>

(Preparation of Polarizer C)

A corona treatment was performed on one surface of an amorphousisophthalic acid-copolymerized polyethylene terephthalate(IPA-copolymerized PET) film substrate (130 μm in thickness) with awater absorption of 0.75% and a Tg of 75° C. An aqueous solutioncontaining polyvinyl alcohol (4,200 in polymerization degree, 99.2% bymole in saponification degree) and acetoacetyl-modified PVA (GohsefimerZ200 (trade name) manufactured by The Nippon Synthetic Chemical IndustryCo., Ltd., 1,200 in polymerization degree, 4.6% in acetoacetylmodification degree, 99.0% by mole or more in saponification degree) ina ratio of 9:1 was applied to the corona-treated surface at 25° C. andthen dried to form a 11-μm-thick PVA-based resin layer, so that alaminate was formed.

Using a simultaneous biaxial stretching machine, the resulting laminatewas shrunk at 110° C. in a first direction (MD) by 30% andsimultaneously stretched in a second direction (TD) to 5.0 times in theair (stretching).

Subsequently, the laminate was immersed in an aqueous iodine solution(iodine concentration: 0.2% by weight, potassium iodide concentration:1.4% by weight) at 25° C. for 40 seconds (dyeing).

The dyed laminate was immersed in an aqueous boric acid solution (boricacid concentration: 5% by weight, potassium iodide concentration: 5% byweight) at 60° C. for 80 seconds (crosslinking).

After the crosslinking, the laminate was immersed in an aqueouspotassium iodide solution (potassium iodide concentration: 5% by weight)at 25° C. for 20 seconds (cleaning).

The resulting product was an optical film laminate including a3-μm-thick polarizer.

(Preparation of One-Side-Protected Polarizing Film C)

A protective film (Z-TAC ZRD40SL (trade name) manufactured by FUJIFILMCorporation, 40 μm in thickness) was bonded to the polarizer side of thelaminate with a vinyl alcohol-based adhesive. Subsequently, theamorphous PET substrate was removed, so that one-side-protectedpolarizing film C having the thin polarizer was obtained. The opticalproperties of resulting one-side-protected film C were as follows:transmittance 38.4%, polarization degree 99.99%.

<One-Side-Protected Polarizing Film D>

(Preparation of Polarizer D (12-μm-Thick Polarizer))

A 30-μm-thick polyvinyl alcohol film with an average degree ofpolymerization of 2, 400 and a degree of saponification of 99.9% by molewas immersed in warm water at 30° C. for 60 seconds so that it wasallowed to swell. Subsequently, the film was immersed in an aqueoussolution of 0.3% iodine/potassium iodide (0.5/8 in weight ratio) anddyed while stretched to 3.5 times. The film was then stretched to atotal stretch ratio of 6 times in an aqueous boric ester solution at 65°C. After the stretching, the film was dried in an oven at 40° C. for 3minutes to give a PVA-based polarizer. The resulting polarizer was 12 μmin thickness.

(Preparation of One-Side-Protected Polarizing Film D)

Similarly to the preparation of one-side-protected polarizing film A,the transparent protective film shown above was bonded to one surface ofthe PVA-based polarizer with the ultraviolet-curable adhesive shownabove. The optical properties of resulting one-side-protected film Dwere as follows: transmittance 42.8%, polarization degree 99.99%.

<Transparent Layer-Forming Material>

(Composition of Acrylic-Based, Layer-Forming Material A)

N-hydroxyethylacrylamide (HEAA (trade name) 12.5 parts manufactured byKOHJIN Film & Chemicals Co., Ltd.) Acryloylmorpholine (ACMO ® (tradename)   25 parts manufactured by KOHJIN Film & Chemicals Co., Ltd.)Dimethylol tricyclodecane diacrylate (LIGHT ACRYLATE 62.5 parts DCP-A(trade name) manufactured by Kyoeisha Chemical Co., Ltd.) Photo-radicalpolymerization initiator   2 parts(2-methyl-1-(4-methylthiophehyl)-2-morpholinopropan-1-one (IRGACURE 907(trade name) manufactured by BASF)) Photosensitizer (diethylthioxanthone (KAYACURE DETX-S   2 parts (trade name) manufactured byNippon Kayaku Co., Ltd.))

(Composition of Acrylic-Based, Layer-Forming Material B)

N-hydroxyethylacrylamide (HEAA (trade name) 20 parts manufactured byKOHJIN Film & Chemicals Co., Ltd.) Urethane acrylate (UV-1700B (tradename) manufactured by 80 parts The Nippon Synthetic Chemical IndustryCo., Ltd.) Photo-radical polymerization initiator  3 parts(2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one (IRGACURE 907(trade name) manufactured by BASF)) Photosensitizer (diethylthioxanthone (KAYACURE DETX-S  2 parts (trade name) manufactured byNippon Kayaku Co., Ltd.))

(Composition of Acrylic-Based, Layer-Forming Material C)

N-hydroxyethylacrylamide (HEAA (trade name) 12.5 parts manufactured byKOHJIN Film & Chemicals Co., Ltd.) 2-hydroxy-3-phenoxypropyl acrylate(ARONIX ® M-5700   25 parts (trade name) manufactured by Toagosei Co.,Ltd.) 1,9-nonanediol diacrylate (LIGHT ACRYLATE 1.9ND-A   40 parts(trade name) manufactured by Kyoeisha Chemical Co., Ltd.) Dimethyloltricyclodecane diacrylate (LIGHT ACRYLATE 22.5 parts DCP-A (trade name)manufactured by Kyoeisha Chemical Co., Ltd.) Photo-radicalpolymerization initiator   3 parts(2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one (IRGACURE 907(trade name) manufactured by BASF)) Photosensitizer (diethylthioxanthone (KAYACURE DETX-S   2 parts (trade name) manufactured byNippon Kayaku Co., Ltd.))

(Composition of Acrylic-Based, Layer-Forming Material D)

N-hydroxyethylacrylamide (HEAA (trade name) 20 parts manufactured byKOHJIN Film & Chemicals Co., Ltd.) Urethane acrylate (UV-3500BA (tradename) Manufactured 80 parts by The Nippon Synthetic Chemical industryCo., Ltd.) Photo-radical polymerization initiator  3 parts(2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one (IRGACURE 907(trade name) manufactured by BASF)) Photosensitizer (diethylthioxanthone (KAYACURE DETX-S  2 parts (trade name) manufactured byNippon Kayaku Co., Ltd.))

(Composition of Acrylic-Based, Layer-Forming Material E)

N-hydroxyethylacrylamide (HEAA (trade name) 12.5 parts manufactured byKOHJIN Film & Chemical. Co., Ltd.) 2-hydroxy-3-phenoxypropyl acrylate(ARONIX ® M-5700   30 parts (trade name) manufactured by Toagosei Co.,Ltd.) 1,9-nonanediol diacrylate (LIGHT ACRYLATE 1.9ND-A   40 parts(trade name) manufactured by Kyoeisha Chemical Co., Ltd.) Dimethyloltricyclodecane diacrylate (LIGHT ACRYLATE 17.5 parts DCP-A (trade name)manufactured by Kyoeisha Chemical Co., Ltd.) Photo-radicalpolymerization initiator   3 parts(2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one (IRGACURE 907(trade name) manufactured by BASF)) Photosensitizer (diethylthioxanthone (KAYACURE DETX-S   2 parts (trade name) manufactured byNippon Kayaku Co., Ltd.))

(Composition of Epoxy-Based, Layer-Forming Material A)

3′,4′-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate (CELLOXIDE2021P (trade name) manufactured by DAICEL CORPORATION) 100 parts

Photo-cation polymerization initiator(4-(phenylthio)phenyldiphenylsulfonium hexafluorophosphate (CPI-100P(trade name) manufactured by SAN-APRO LTD.) 1 part

(Preparation of Active Energy Ray-Curable, Layer-Forming Materials)

Each active energy ray-curable, layer-forming material was prepared bymixing each of acrylic-based, layer-forming materials A to E orepoxy-based, layer-forming material A and stirring them at 50° C. for 1hour.

(Composition of Isocyanate Layer-Forming Material A)

A urethane prepolymer coating liquid was prepared by adding 50 parts ofa 75% ethyl acetate solution of a urethane prepolymer of xylylenediisocyanate and trimethylolpropane (TAKENATE D110N (trade name)manufactured by Mitsui Takeda Chemicals Inc.) and 0.1 parts of adioctyltin dilaurate-based catalyst (EMBILIZER OL-1 (trade name)manufactured by Tokyo Fine Chemical CO., LTD.) to 50 parts of a 75%ethyl acetate solution of a urethane prepolymer of tolylene diisocyanateand trimethylolpropane (CORONATE L (trade name) manufactured by TosohCorporation) and adjusting the solid concentration of the mixture to 35%with methyl isobutyl ketone as a solvent.

(Polyvinyl Alcohol-Based, Layer-Forming Material A)

An aqueous solution with a solid concentration of 4% by weight wasprepared by dissolving a polyvinyl alcohol resin with a polymerizationdegree of 2,500 and a saponification degree of 99.0 mol % (JC-25 (tradename) manufactured by JAPAN VAM & POVAL CO., LTD.) in pure water.

(Polyvinyl Alcohol-Based, Layer-Forming Material B)

An aqueous solution with a solid concentration of 4% by weight wasprepared by dissolving a polyvinyl alcohol resin with a polymerizationdegree of 2,000 and a saponification degree of 99.4 mol % (NH-20 (tradename) manufactured by The Nippon Synthetic Chemical Industry Co., Ltd.)in pure water.

(Polyvinyl Alcohol-Based, Layer-Forming Material C)

An aqueous solution with a solid concentration of 4% by weight wasprepared by dissolving a polyvinyl alcohol resin with a polymerizationdegree of 1,700 and a saponification degree of 97.0 mol % (AH-17 (tradename) manufactured by The Nippon Synthetic Chemical Industry Co., Ltd.)in pure water.

(Polyvinyl Alcohol-Based, Layer-Forming Material D)

An aqueous solution with a solid concentration of 4% by weight wasprepared by dissolving a polyvinyl alcohol resin with a polymerizationdegree of 1,700 and a saponification degree of 99.0 mol % (PVA117 (tradename) manufactured by KURARAY CO., LTD.) in pure water.

(Polyvinyl Alcohol-Based, Layer-Forming Material E)

An aqueous solution with a solid concentration of 4% by weight wasprepared by dissolving a polyvinyl alcohol resin with a polymerizationdegree of 4,000 and a saponification degree of 99.0 mol % (JC-40 (tradename) manufactured by JAPAN VAM & POVAL CO., LTD.) in pure water.

<Formulation of Pressure-Sensitive Adhesive Layer>

A reaction vessel equipped with a condenser tube, a nitrogen inlet tube,a thermometer, and a stirrer was charged with 100 parts of butylacrylate, 3 parts of acrylic acid, 0.1 parts of 2-hydroxyethyl acrylate,0.3 parts of 2,2′-azobisisobutyronitrile, and ethyl acetate, so that asolution was obtained. Subsequently, the solution was allowed to reactat 55° C. for 8 hours under stirring with nitrogen gas being blown intothe solution, so that a solution containing an acryl-based polymer witha weight average molecular weight of 2,200,000 was obtained. Ethylacetate was further added to the acryl-based polymer-containing solutionto form an acryl-based polymer solution with an adjusted solidconcentration of 30%.

A pressure-sensitive adhesive solution was prepared by adding 0.5 partsof a crosslinking agent (CORONATE L (trade name) manufactured by NipponPolyurethane Industry Co., Ltd.) including an isocyanategroup-containing compound as a main component and 0.075 parts ofγ-glycidoxypropyltrimethoxysilane (KBM-403 (trade name) manufactured byShin-Etsu Chemical Co., Ltd.) as a silane coupling agent in this orderto the acryl-based polymer solution based on 100 parts of the solids ofthe acryl-based polymer solution. The pressure-sensitive adhesivesolution was applied to the surface of a release sheet (separator) madeof a release-treated polyethylene terephthalate film (38 μm inthickness) in such a manner that a 25-μm-thick coating could be formedafter drying, and then dried to form a pressure-sensitive adhesivelayer.

Example 1

<Preparation of Transparent Layer-Attached, One-Side-ProtectedPolarizing Film>

Using a wire bar coater, the active energy ray-curable, layer-formingmaterial (acrylic-based, layer-forming material A) was applied to thepolarizer surface of one-side-protected polarizing film A (the polarizersurface opposite to the surface provided with the transparent protectivefilm) to form a 1-μm-thick coating. Under a nitrogen atmosphere, activeenergy rays were then applied to the coating, so that a transparentlayer-attached, one-side-protected polarizing film was obtained. In thisprocess, active energy rays were applied using the same means as in thepreparation of one-side-protected polarizing film A.

<Preparation of Pressure-Sensitive-Adhesive-Layer-Attached PolarizingFilm>

Subsequently, the pressure-sensitive adhesive layer formed on therelease-treated surface of the release sheet (separator) was attached tothe transparent layer formed on the one-side-protected polarizing film,so that a pressure-sensitive-adhesive-layer-attached polarizing film wasobtained.

Examples 2 to 24 and Comparative Examples 1 to 13

One-side-protected polarizing films, transparent layer-attachedone-side-protected polarizing films, andpressure-sensitive-adhesive-layer-attached polarizing films wereprepared as in Example 1, except that the type of the one-side-protectedpolarizing film, the transparent layer-forming material, and thethickness of the transparent layer were changed as shown in Table 2.

Note that in Example 13, a 1-μm-thick urethane resin layer was formed asthe transparent layer by applying isocyanate A (a urethane prepolymercoating liquid) to the polarizer surface of one-side-protected film Awith a bar coater and then heat-treating the coating at 60° C. for 12hours.

When each polyvinyl alcohol-based, layer-forming material was used, thelayer-forming material adjusted to 25° C. was applied in such a mannerthat a coating with the thickness shown in Table 2 could be formed afterdrying, and then dried with hot air at 60° C. for 1 minute, so that atransparent layer-attached one-side-protected polarizing film wasobtained.

The pressure-sensitive-adhesive-layer-attached polarizing films obtainedin the examples and the comparative examples were evaluated as describedbelow. The results are shown in Table 2.

<Single-Body Transmittance T and Polarization Degree P of Polarizer>

The single-body transmittance T and polarization degree P of theresulting one-side-protected polarizing films were measured using anintegrating sphere-equipped spectral transmittance meter (DOT-3Cmanufactured by Murakami Color Research Laboratory Co., Ltd.).

The polarization degree P is calculated from the formula below using thetransmittance (parallel transmittance Tp) of a laminate of the same twopolarizing films with their transmission axes parallel to each other andthe transmittance (crossed transmittance Tc) of a laminate of the sametwo polarizing films with their transmission axes orthogonal to eachother. Polarization degree P (%)={(Tp−Tc)/(Tp+Tc)}^(1/2)×100

Each transmittance was expressed as the Y value, which was obtainedthrough luminosity correction using the two-degree field (illuminant C)according to JIS Z 8701 when the transmittance for completely polarizedlight obtained through a Glan-Taylor prism polarizer was normalized to100%.

<Measurement of the Content of Boric Acid in Polarizer>

The polarizers obtained in the examples and the comparative exampleswere subjected to attenuated total reflection (ATR) spectroscopy usingpolarized light as the measurement light and using a Fourier transforminfrared spectrometer (FTIR) (Spectrum 2000 (trade name) manufactured byPerkinElmer, Inc.), in which the boric acid peak (665 cm⁻¹) intensityand the reference peak (2,941 cm⁻¹) intensity were measured. The boricacid amount index was calculated from the formula below using theresulting boric acid peak intensity and reference peak intensity, andthen the boric acid content (% by weight) was determined from theformula below using the calculated boric acid amount index.(Boric acid amount index)=(the intensity of the boric acid peak at 665cm⁻¹)/(the intensity of the reference peak at 2,941 cm⁻¹)(Boric acid content (% by weight))=(boric acid amount index)×5.54+4.1

<Measurement of Compressive Elastic Modulus at 80° C.>

The compressive elastic modulus was measured using TI900 TriboIndenter(manufactured by Hysitron Inc.). A piece with a size of 10 mm×10 mm wascut from resulting transparent layer-attached, one-side-protectedpolarizing film 11, then fixed on the support attached to TriboIndenter,and then subjected to the measurement of compressive elastic modulus bynanoindentation method. In the measurement, the position of the indenterwas so adjusted that it would indent a portion at or near the center ofthe transparent layer. The measurement conditions are shown below.

Indenter used: Berkovich (triangular pyramid type)

Measurement method: single indentation measurement

Measurement temperature: 80° C.

Indentation depth setting: 100 nm

<Suppression of Expansion of Nano-Slits (Rock and Roll Test)>

In this test, scratches were formed on polarizer 1 of one-side-protectedpolarizing film 10 by the method described below, before the transparentlayer was formed in each of the examples and the comparative examples.Thereafter, transparent layer-attached one-side-protected polarizingfilm 11 was prepared.

Subsequently, after transparent layer-attached one-side-protectedpolarizing film 11 was allowed to stand in an environment at 80° C. for1 hour, it was evaluated whether light-leaking cracks occurred in sample11, based on the following criteria.

A: no cracks

B: 1 to 100 cracks

C: 101 to 200 cracks

D: 201 or more cracks

<<How to Form Scratches>>

A piece with a size of 50 mm×150 mm (50 mm in the absorption axisdirection) was cut from resulting one-side-protected polarizing film 10.Sample 10 used was a laminate obtained by bonding surface protectivefilm 6 for test to the transparent protective film 2 side of the cutpiece. Surface protective film 6 for test was prepared by the methoddescribed below.

(Surface Protective Film for Test)

A backing-forming material of low-density polyethylene with a melt flowrate of 2.0 g/10 min at 190° C. and a density of 0.924 g/cm³ wassupplied to an inflation molding machine for co-extrusion.

At the same time, a pressure-sensitive adhesive-forming material of apropylene-butene copolymer (propylene:butene=85:15 in weight ratio,atactic structure) with a melt flow rate of 10.0 g/10 min at 230° C. anda density of 0.86 g/cm³ was supplied to the inflation molding machinewith a die temperature of 220° C. and subjected to co-extrusion. Asurface protective film composed of a 33-μm-thick backing layer and a5-μm-thick pressure-sensitive adhesive layer was produced in this way.

As illustrated in the schematic view of FIG. 5A and the cross-sectionalview of FIG. 5B, two glass supports 21 of 25 mm wide×150 mm long×5 mmhigh were placed parallel at a distance of 115 mm between their innersides on a substrate 20 (65 mm wide×165 mm long×2 mm high). Sample 11obtained through the cutting was placed in such a manner that thedirection perpendicular to the absorption axis of polarizer 1 of sample11 was parallel to the longitudinal direction of the two glass supportsand both sides of sample 11 were evenly supported on the two glasssupports. Sample 11 was placed with surface protective film 6 facingupward.

Subsequently, a load of 100 g was applied from a guitar pick (Model No.HP2H (HARD) manufactured by HISTORY) to the center of sample 10 (surfaceprotective film 6 side), and the applied load was reciprocated 10 timeswithin a distance of 100 mm in the direction perpendicular to theabsorption axis of polarizer 1 of sample 11, so that scratches wereformed on the surface of polarizer 1. The load was applied to oneportion. Subsequently, it was visually observed whether or notnano-slits occurred.

The films of Comparative Examples 3 to 6, in which the polarizer had athickness of more than 10 μm, were broken upon the formation ofnano-slits in the rock and roll test due to high shrinkage stress insidethe polarizer. This made the evaluation impossible.

FIGS. 6A and 6B are each an exemplary micrograph of the polarizing filmsurface, which provides the measure below for identifying light-leakingcracks (nano-slits a) in the rock and roll testing of one-side-protectedpolarizing film 10 or transparent layer-attached one-side-protectedpolarizing film 11. In FIG. 6A, any light-leaking cracks caused bynano-slits a are not found. The state shown in FIG. 6A corresponds tothe state before the heating in the rock and roll test on the examples,and the state after the heating in the rock and roll test on theexamples (nano-slits do not cause light leakage due to theexpansion-suppressing effect). On the other hand, FIG. 6B shows a casewhere three light-leaking cracks occur in the direction of theabsorption axis of the polarizer due to nano-slits a formed by heating.The state shown in FIG. 6B corresponds to the state after the heating inthe rock and roll test on the comparative examples. FIGS. 6A and 6B wereobtained by observing the samples suffering from nano-slits using adifferential interference microscope. When each sample was photographed,another sample with no nano-slits was placed on the lower side(transmitted light source side) of the sample suffering from nano-slitsin such a manner that they were in a crossed-Nicols arrangement, andthen they were observed with transmitted light.

<Observation of Through Cracks (Heat Shock Test)>

A piece of 50 mm×150 mm (50 mm in the absorption axis direction) and apiece of 150 mm×50 mm (150 mm in the absorption axis direction) were cutfrom each resulting pressure-sensitive-adhesive-layer-attachedpolarizing film. The cut pieces were bonded in the directions of crossedNicols to both sides a 0.5-mm-thick non-alkali glass sheet to form asample. The sample was exposed to the environment of 100 cycles of heatshock from −40 to 85° C. each for 30 minutes. Subsequently, the samplewas taken out and visually observed for the presence or absence ofthrough cracks (and the number of through cracks) in thepressure-sensitive-adhesive-layer-attached polarizing film. This testwas performed five times. The evaluation was performed according to thefollowing.

◯: No through crack is observed.

x: A through crack or cracks are observed.

FIG. 7 is an exemplary micrograph of the polarizing film surface, whichprovides a measure for identifying a through crack b inone-side-protected polarizing film 10 or transparent layer-attachedone-side-protected polarizing film 11. FIG. 7 was obtained by observingthe sample suffering from a through crack using a differentialinterference microscope.

<Moist Heat Resistance (Rate of Change in Polarization Degree (OpticalReliability Test))>

A piece with a size of 25 mm×50 mm (50 mm in the absorption axisdirection) was cut from each resulting one-side-protected polarizingfilm. The cut piece (sample) of the one-side-protected polarizing filmwas stored in a thermo-hygrostat at 85° C. and 85% RH for 150 hours. Thepolarization degree of the one-side-protected polarizing film sample wasmeasured before and after the storage using an integratingsphere-equipped spectral transmittance meter (DOT-3C manufactured byMurakami Color Research Laboratory Co., Ltd.), and used for thecalculation of: rate (%) of change in polarization degree=(1−(thepolarization degree after the storage)/(the polarization degree beforethe storage)).

The polarization degree P is calculated from the formula below using thetransmittance (parallel transmittance Tp) of a laminate of the same twopolarizing films with their transmission axes parallel to each other andthe transmittance (crossed transmittance Tc) of a laminate of the sametwo polarizing films with their transmission axes orthogonal to eachother. Polarization degree P (%)={(Tp−Tc)/(Tp+Tc)}^(1/2)×100

Each transmittance was expressed as the Y value, which was obtainedthrough luminosity correction using the two-degree field (illuminant C)according to JIS Z 8701 when the transmittance for completely polarizedlight obtained through a Glan-Taylor prism polarizer was normalized to100%.

TABLE 2 One-side-protected polarizing film Polarizer Single-bodyPolarization Boric acid Thickness transmittance degree P contentTransparent resin layer Type (μm) T (%) (%) (wt %) Material Example 1 A05 42.8 99.99 16 Acrylic A Example 2 A0 5 42.8 99.99 16 Acrylic A Example3 A0 5 42.8 99.99 16 Acrylic B Example 4 A0 5 42.8 99.99 16 Acrylic BExample 5 A0 5 42.8 99.99 16 Acrylic B Example 6 A0 5 42.8 99.99 16Acrylic B Example 7 A0 5 42.8 99.99 16 Polyvinyl Alcohol A Example 8 A05 42.8 99.99 16 Polyvinyl Alcohol A Example 9 A0 5 42.8 99.99 16Polyvinyl Alcohol A Example 10 A0 5 42.8 99.99 16 Acrylic C Example 11A0 5 42.8 99.99 16 Acrylic C Example 12 A4 5 42.8 99.99 16 Acrylic BExample 13 A5 5 42.8 99.99 16 Acrylic B Example 14 A1 5 42.8 99.99 14Acrylic B Example 15 A2 5 42.8 99.99 18 Acrylic B Example 16 A3 5 42.899.99 20 Acrylic B Example 17 A6 5 44.1 99.99 16 Acrylic B Example 18 A75 41.5 99.99 16 Acrylic B Example 19 A0 5 42.8 99.99 16 Epoxy A Example20 A0 5 42.8 99.99 16 Isocyanate A Example 21 A0 5 42.8 99.99 16Polyvinyl Alcohol B Example 22 A0 5 42.8 99.99 16 Polyvinyl Alcohol CExample 23 A0 5 42.8 99.99 16 Polyvinyl Alcohol D Example 24 A0 5 42.899.99 16 Polyvinyl Alcohol E Comparative A0 5 42.8 99.99 16 AbsentExample 1 Comparative A0 5 42.8 99.99 16 Acrylic E Example 2 ComparativeB 23 42.8 99.99 16 Acrylic A Example 3 Comparative B 23 42.8 99.99 16Acrylic D Example 4 Comparative B 23 42.8 99.99 16 Epoxy A Example 5Comparative D 12 42.8 99.99 16 Absent Example 6 Comparative A4 3 42.899.99 16 Absent Example 7 Comparative A5 7 42.8 99.99 16 Absent Example8 Comparative A1 5 42.8 99.99 16 Absent Example 9 Comparative A6 5 44.199.99 16 Absent Example 10 Comparative A7 5 41.5 99.99 16 Absent Example11 Comparative C 3 38.4 99.99 16 Absent Example 12 Comparative A8 3.543.2 99.15 16 Absent Example 13 Evaluation Transparent resin layerSupression Compressive of expansion Observation Optical elastic ofnano-slits of through reliability modulus C Thickness (rock and crack(heat (65° C., 85% RH, (GPa) (μm) roll test) shock test) 150 hours)Example 1 10.01 1 A ∘ 0.42% Example 2 10.01 0.2 A ∘ 0.18% Example 3 5.443 A ∘ 1.67% Example 4 5.44 1 A ∘ 0.58% Example 5 5.44 6 A ∘ 3.22%Example 6 5.44 0.2 A ∘ 0.14% Example 7 2.12 3 A ∘ 1.04% Example 8 2.12 1A ∘ 0.06% Example 9 2.12 0.2 A ∘ 0.09% Example 10 0.2 3 C ∘ 1.55%Example 11 0.2 1 C ∘ 0.27% Example 12 5.44 1 A ∘ 0.21% Example 13 5.44 1A ∘ 0.23% Example 14 5.44 1 A ∘ 0.41% Example 15 5.44 1 A ∘ 0.44%Example 16 5.44 1 A ∘ 0.51% Example 17 5.44 1 A ∘ 0.15% Example 18 5.441 A ∘ 0.60% Example 19 3.6 1 A ∘ 2.21% Example 20 0.92 1 B ∘ 1.38%Example 21 0.14 1 A ∘ 0.05% Example 22 3.41 1 A ∘ 1.46% Example 23 4.341 A ∘ 0.30% Example 24 7.13 1 A ∘ 0.08% Comparative Absent D ∘ 0.10%Example 1 Comparative 0.01 6 D ∘ 2.66% Example 2 Comparative 5.44 3Impossible x No data Example 3 to evaluate Comparative 0.02 6 Impossiblex No data Example 4 to evaluate Comparative 3.6 7 Impossible ∘ No dataExample 5 to evaluate Comparative Absent Impossible x No data Example 6to evaluate Comparative Absent D ∘ 0.03% Example 7 Comparative Absent D∘ 0.19% Example 8 Comparative Absent D ∘ 0.45% Example 9 ComparativeAbsent D ∘ 0.09% Example 10 Comparative Absent D ∘ 0.44% Example 11Comparative Absent Not ∘ No data Example 12 occurring Comparative AbsentNot ∘ No data Example 13 occurring

The problems to be solved by the disclosure (the occurrence of throughcracks and nano-slits) did not occurred when the optical propertiesrepresented by the single-body transmittance T and the polarizationdegree P did not satisfy the condition of the following formula:P>−(10^(0.929T−42.4)−1)×100 (provided that T<42.3) or P≥99.9 (providedthat T≥42.3), as in Comparative Example 12 or 13.

Example 25

Example 25 was similar to Example 1, except that the one-side-protectedpolarizing film was used in the form of a long strip, the layer-formingmaterial was applied using a micro-gravure coater, and the release sheet(separator) and the surface protective film described below were used inthe form of long strips. The resulting products were rolls of thetransparent layer-attached one-side-protected polarizing film (with thestructure shown in FIG. 2(A)) having the separator placed on thetransparent layer side and having the surface protective film placed onthe transparent protective film side. A set of rolls of the transparentlayer-attached one-side-protected polarizing film were provided havingwidths corresponding to the short and long sides of a 32-inch non-alkaliglass sheet, respectively, in order to be subjected to slit processing,in which the transparent layer-attached one-side-protected polarizingfilm was cut into pieces while being fed continuously.

(Surface Protective Film for Roll-to-Panel Process)

A surface protective film was obtained by applying an acrylicpressure-sensitive adhesive with a thickness of 15 μm to the surface ofan antistatic treatment layer-attached polyethylene terephthalate film(Diafoil T100G38 (trade name) manufactured by Mitsubishi Plastics, Inc.,38 μm in thickness) opposite to its antistatically treated surface.

Using a continuous production system for the roll-to-panel process shownin FIG. 8, the transparent layer-attached one-side-protected polarizingfilms were continuously supplied from the set of rolls, and thetransparent layer-attached one-side-protected polarizing films werecontinuously bonded in a cross-Nicols relationship to both sides of eachof 100 sheets of 0.5-mm-thick 32-inch non-alkali glass.

Examples 26 to 28

Examples 26 to 28 were similar to Example 25, except that thetransparent layer-attached one-side-protected polarizing films wereprepared by methods similar to those in Examples 2, 4 and 8,respectively.

<Observation of Occurrence of Nano-Slits (Heating Test)>

A hundred sheets of non-alkali glass each provided with the transparentlayer-attached one-side-protected polarizing films bonded to both sideswere placed in an oven at 80° C. for 24 hours and then visually observedfor the presence or absence of nano-slits. No nano-slit-induced defect(light leakage) was observed in any of Examples of 25 to 28.

DESCRIPTION OF REFERENCE SIGNS

-   -   1 Polarizer    -   2 Transparent protective film    -   3 Transparent layer    -   4 Pressure-sensitive adhesive layer    -   5, 5 a, 5 b Separator    -   6, 6 a, 6 b Surface protective film    -   10 One-side-protected polarizing film    -   11 One-side-protected polarizing film (with transparent layer)    -   12 Pressure-sensitive-adhesive-layer-attached polarizing film    -   20 a, 20 b Roll of pressure-sensitive-adhesive-layer-attached        polarizing film (roll)    -   21 a, 21 b    -   Pressure-sensitive-adhesive-layer-attached polarizing film (with        surface protective film)    -   100 System for continuously producing image display devices    -   101 a, 101 b Polarizing film supply unit    -   151 a, 151 b Unwinding unit    -   152 a, 152 b Cutting unit    -   153 a, 153 b Peeling unit    -   154 a, 154 b Winding unit    -   201 a, 201 b Bonding unit    -   300 Orientation changing unit    -   P Image display panel    -   X Image display panel feed unit

The invention claimed is:
 1. A one-side-protected polarizing film,comprising: a polarizer; a transparent protective film provided on onlyone surface of the polarizer; and a transparent layer provided directlyon another surface of the polarizer, wherein the polarizer comprises apolyvinyl alcohol-based resin, has a thickness of 10 μm or less, and isdesigned to have a single-body transmittance T and a polarization degreeP representing optical properties satisfying the condition of thefollowing formula: P>−(10^(0.929T−42.4)−1)×100 (provided that T<42.3) orP≥99.9 (provided that T≥42.3), and the transparent layer has an 80° C.compressive elastic modulus of 0.1 GPa or more.
 2. Theone-side-protected polarizing film according to claim 1, wherein thetransparent layer is a product formed from a resin material.
 3. Theone-side-protected polarizing film according to claim 1, wherein thetransparent layer has a thickness of less than 3 μm.
 4. Theone-side-protected polarizing film according to claim 1, wherein thepolarizer contains 25% by weight or less of boric acid based on thetotal weight of the polarizer.
 5. Apressure-sensitive-adhesive-layer-attached polarizing film comprising:the one-side-protected polarizing film according to claim 1; and apressure-sensitive adhesive layer.
 6. Thepressure-sensitive-adhesive-layer-attached polarizing film according toclaim 5, wherein the pressure-sensitive adhesive layer is provided onthe transparent layer of the one-side-protected polarizing film.
 7. Thepressure-sensitive-adhesive-layer-attached polarizing film according toclaim 5, wherein the pressure-sensitive adhesive layer is provided onthe transparent protective film of the one-side-protected polarizingfilm.
 8. The pressure-sensitive-adhesive-layer-attached polarizing filmaccording to claim 5, further comprising a separator provided on thepressure-sensitive adhesive layer.
 9. Thepressure-sensitive-adhesive-layer-attached polarizing film according toclaim 8, which is in the form of a roll.
 10. An image display devicecomprising the one-side-protected polarizing film according to claim 1.11. A method for continuously producing an image display device, themethod comprising the steps of: unwinding thepressure-sensitive-adhesive-layer-attached polarizing film from the rollof the pressure-sensitive-adhesive-layer-attached polarizing filmaccording to claim 9; feeding thepressure-sensitive-adhesive-layer-attached polarizing film with theseparator; and continuously bonding thepressure-sensitive-adhesive-layer-attached polarizing film to a surfaceof an image display panel with the pressure-sensitive adhesive layerinterposed therebetween.
 12. An image display device comprising thepressure-sensitive-adhesive-attached polarizing film according to claim5.
 13. A method for producing the one-side-protected polarizing filmaccording to claim 1, comprising: the polarizer; the transparentprotective film provided on only one surface of the polarizer; and thetransparent layer provided directly on another surface of the polarizer,wherein the polarizer comprises a polyvinyl alcohol-based resin, has athickness of 10 μm or less, and is designed to have a single-bodytransmittance T and a polarization degree P representing opticalproperties satisfying the condition of the following formula:P>−(10^(0.929T−42.4)−1)×100 (provided that T<42.3) or P≥99.9 (providedthat T≥42.3), the transparent layer has an 80° C. compressive elasticmodulus of 0.1 GPa or more, and the transparent layer is provided byapplying directly a transparent layer-forming material on anothersurface of the polarizer.